"It’s fun to play in tight wet holes, but use the proper protection!"
Bolting For Caving
Welcome to our free guide about bolting. This project is our way of contributing to the greater community. It's nice to understand what you are clipping and trusting with your life, even if you never plan on installing or removing bolts. We believe that if someone is going to spend their time and money to bolt something, they probably want to do it as good as possible. Hopefully, the Bolting Bible gives you the tools you need to do a great job.
This book is in a blog format. The main blog points to all 17 chapters, and at the end of each chapter, it points you to the next. A downloadable pdf is available HERE.
A huge thanks to Rachel S. for contributing so much information and so much old-bolt porn to this section Also, thank you John Fioroni of Cave Exploration Society / ExtremeGear.org, as well as Big Name Pit Bouncer Ethan Reuter for your contributions.
Who Should Read This...?
The audience is cavers of any skill-level, as well as prospective cavers. You should do your own homework, seek education from multiple resources, and draw your own conclusions. The goal is that everyone / anyone is capable of making educated decisions about THEIR safety, rather than be at the mercy of someone else’s idea of it.
This is not an all-encompassing textbook on the subject of permanent fixed anchors and it does not delve into the gear and systems necessary for doing single rope technique (SRT) a.k.a. vertical caving. While it does speak generally to rigging ropes, the chapter is merely used to contextualize the "why's" of bolting and give historical context to the evolution of caving as an activity and as a community.
Leave Less Trace
Caves are kept hush-hush for a reason. It's pretty devastating when people don't respect them. It takes a gazillion years for anything to go back to its natural state if people fuck-up the fragile ecosystems, break cave formations, damage features, or just leave a footprint. So please think before installing a bolt. On the flipside, adding hardware can actually help preserve an area by providing a dedicate route for ropework and thus avoiding unintentionally stripping flora/fauna from cave walls, smashing speleothems, or dislodging loose rocks from the walls.
Think holistically about your impact.
Legalese
Are you allowed to bolt??? Who owns or manages that cave? Are you on public lands? If so, are those Federally designated areas..?
Know your area first before installing permanent hardware in it-- you could potentially fuck things over very badly for other cavers.
Once you know where you are, think of who else is involved: Is the cave a managed site, such as a cave preserve or within a state / national park? Is there an established process (ex/ Special Use Permits) for adding / updating hardware, ropes, etc.? Is there an active mapping or exploration project going on, and who should have input? If it is a new cave discovery, chances are it's not actually new (it's probably just new to you). Again, know your area and the community of cavers first.
Cave Rock
Unlike aboveground cliffs and crags, cave rock has not been exposed to millenia of weathering from rain, wind, freeze/thaw cycles, etc. Imagine killer flakes glued to the wall by only mud, or 6-ft tall “leaning towers” of choss that collapse when touched, and all the pretty cave cancer that you see pictures of.
Caves can be formed in several ways, but the most common is surface water slowly dissolving limestone. Limestone is mostly dead sea creatures glued together with pressure and time and is generally considered a soft rock. It's not as soft as some sandstone, but softer than some bomber granite. The exposed walls of a cave may be very uniform like poured concrete, or it might just be layered with good rock, then bad rock, then good rock, so-on-and-so-forth, ...oooor it could be a total hellscape with death-flakes peeling off!
Don't Wallow In The Mud
You don't always get easy access to the rock. Walls may also have a layer of mud … if not a heavy layer of mud. It is not rare to see walls with >4 inches deep of heavy mud that must be scraped clean before hitting actual rock. It will take extra effort to clear enough mud off the wall to be able to hear from the hammer strike if the rock below it is bomber. Be mindful to not spatter mud in your eyes because that sucks.
See a real example of navigating mud and installing bolts in a cave
Rock Buffet
Due to the nature of speleogenesis and hydrology, caves often follow structural weaknesses in the bedrock– structural (faults, joints, fractures) or compositional (weaker rock types). Therefore, it isn't surprising that the rock creating the cave passage could be chossy (shaley, poorly compacted), or structurally fucked up (semi-collapsed, flaked, fractured). Within any given cave wall, it is common to see bands of different quality rock; some layers are more structurally sound than others.
It is absolutely imperative to use a hammer to test the rock before bolting because voids or flaking can exist without being visible. Smack the rock, hard, and listen for hollow / flat / dull sounds-- those are bad.
A bolt is only as good as the rock in which it is placed.
Limestone - yup, that's most caves
Just to restate the basics: most caves are limestone. Limestone is a sedimentary rock and comes in a sweeping variety of compositions. It can also have other layers of rock mixed through it, and/or have globs / nodules / chunkies of weird stuff (like chert) interspersed within it.
In some regions, the limestone can be unboltable because of its high porosity and/or loose compaction. That said, such loosey-goosey bedrock typically means that vertical cave development is not common either and thus we can simply disregard the existence of those crumbly horizontal caves.
Shales and Sandstone - Avoid it
Underground, sandstone is often not "purely sandstone" but rather a sandstone-rich limestone. Broadly speaking, it is simply crappy rock due to a number of factors including its material composition and the fact that it is totally saturated by moisture. When selecting a bolt placement, cave sandstone should be approached with caution if not avoided all together.
Shale layers are often found between units of limestone, or limestone-sandstone interfaces. Thankfully, it is very easy to identify the shaley rocks in a given cave wall because they'll look like a crumbly chossy mess and will likely fall apart when smacked with the bolting hammer.
Chert - Unboltable
Chert, commonly called flint, is the mineral form of silicon dioxide (SiO2), which in English means “evil sharp rocks” and it doesn’t dissolve in water like limestone. It is extremely brittle because it is literally globs of glass that are not structurally sound and it cannot be used for bolt placements. Attempting to drill into it could even break the carbide tip off of the drill bit. Chert can be thick layers, huge blobs, or chunkies in a band of bedrock which should be avoid (if possible) in favor of a more uniform section of limestone.
Calcite - Sketchy
Flowstone (calcite) is formed when limestone is dissolved by water and then redeposited to make all that cool flowy-lookin’ stuff that you imagine when thinking about caves. The umbrella terms for stalactites, stalagmites, bacons, and delicate-shinies are “formations” or if you want to sound super fancy, “speleothems.” The color varies depending on what other minerals are mixed-in with the calcite; it can be white, black, orange, yellow, etc.
Regardless of its shape, the flowstone itself is often porous like a sponge, or heavily layered like book pages, it may be full of voids (pockets), and/or could be completely hollow and can sing like a wind chime when thumped. Therefore, the bolt placements are marginal because of how it's layered: imagine putting a screw in a phone book instead of a block of wood.
An additional sketch factor for flowstone is where it can form; basically "anywhere." While it could be formed over a really bomber foundation of bedrock, it could just as well be a "candy-coating" encrusting mud or gravel or sand, or all of the above. In short: it is often total shit-quality rock and may not even be firmly attached to the cave walls.
If there is a solid wall behind the flowstone coating, and there are no other options, then proceed with caution and use safeguards such as sleeve bolts or glue-ins. Longer bolts are ideal, too, because the hardware needs to reach into the solid rock behind the flowstone crust.
All that said: keep in mind that damaging cave formations can have serious legal repercussions, plus it is just an asshole thing to do!
Tools
Rotary hammer drills: Most quality brand roto-hammers can handle some water, but none are waterproof. Additionally, mud can kill the drill by clogging the vents and causing it to overheat. The brands of drills we kill the least underground are Hilti, DeWalt, and Bosch-- these brands tend to be heavier in weight and use larger batteries. The featherweights of the professional line, Milwaukee and Makita subcompacts, are cave tolerant but might not survive the trauma a Hilti can endure...
Manual hammers: absolutely necessary -- always test the rock before drilling. Light-duty bolting hammers are recommended; piton hammers are fairly oversized for caves. Several of the hammers, such as the Raumer Action and Petzl TamTam, have a socket in the end to tighten nuts. The stock socket size is 13mm (for 8mm bolts), but 17mm adapters are available (for 10mm bolts).
Blow tube and bolt brush: no excuse for not using these -- they weigh almost nothing and it takes less than 30 seconds to clean hole.
Lastly, you should already be carrying a standard 6" adjustable wrench in your vertical caving kit, and you'll need that wrench for properly tightening the nut. Try to keep it clean, though-- it's easy to get it too muddy to work properly.
As a reminder: everything should have a tether in case you drop a tool. Do not bring a drill (or anything, honestly) into a cave unless you are okay with it being destroyed. For more information about the basic needs for bolting, see the Book of Holes section of the Bolting Bible.
Rigging, Ropes, and Limitations
Going vertical requires rigging ropes and ropes need anchors. The theory behinds anchoring ropes for divides into two main categories: naturals and bolts. Historically in the US, bolts were shunned in favor of natural-only rigging. While there is some justification for the skepticism of the classic bolts from yester-year (see later section), modern bolts are the most consistent and reliable form of permanent anchors.
So why bolt? It would be great if every pit had a handy-dandy natural rigging point at the edge of it … but that’s not reality. We typically get lucky with open air pits and can rig on big f***ing trees (BFTs), but once inside the cave the options for naturals is a crapshoot.
The golden concept: The goal of (proper) bolting is to create totally free-hanging drops (i.e. no rub points) which allows the use of lighter ropes (usually 9mm) and no additional rope protection because the rope is reanchored or deviated at rub-points. This method is loosely called alpine rigging.
To the contrary, when when ropes are not free-hanging, thick (11mm) heavy-sheathed abrasion-resistant rope (such as PMI MaxWear, aka pit rope) are used in conjunction with rope pads to withstand the abuse. This is called "indestructible rope technique" (IRT).
Historically, caving in the US was based on indestructible rope technique (IRT). However, this has been rapidly changing since the late 2010s as more young cavers become increasingly interested in technical ropework.
At this point, you may be wondering why there is so much focus on rope types– after all, this is Bolting Bible. The entire concept of bolting is meaningless without explaining the types of ropes used in caving. This information may seem tedious but it is absolutely crucial.
More thoughts: Environmental risk factors should be strongly considered when assessing whether or not to bolt, such as the potential for rock fall and/or the danger associated with doing ropework in active water. Rigging in waterfalls is arguably the most dangerous vertical situation encountered underground; hypothermia on rope has caused a multitude of near-misses (many go unreported), as well as several fatalities.
Alpine versus IRT: which is more efficient?
There is no blanket answer to this question because it is very situational based on the cave, the skillset of the cavers, etc. It may actually be better to leave a pit “natural” if bolting does not create a free-hanging drop because we are already damned to use pit rope anyway.
Using IRT and rope pads is often slower than crossing a rebelay because each person has to reset the rope pad and negotiate the lip of the pit. However, bolting rebelays is demanding on hardware ($$$) consumption and uses more footage of rope. Rope pads can be extremely efficient if they are attached to the wall rather than tied onto the rope, but it is common for issues to arise due to rope stretch, user error, etc. Your mileage will vary.
From a gear transportation / logistics viewpoint, the size of big pit rope is not the only downside to using IRT rigging methods-- rope pads will also be needed. While packing rope pads for an entrance drop isn’t much trouble, the additional bulkiness and weight is increased substantially for deep systems with many vertical sections.
All of this may sound like a lot of fussing (i.e. ultralight jerking-off), especially for those who have not been in many caves. However, using huge pit rope versus lightweight “alpine” rope can dramatically change situation. While hiking aboveground with a bulky pack weighing >30-lb is no struggle, cave packs are rarely staying on one's back underground. Instead, cavers typically deal with hours of cramming their packs (and themselves) through grim passages barely person-sized, and/or dead-dragging it through belly-crawls.
If pack size and weight is such an issue, it seems logical to simply split up the gear into smaller loads and bring more people. Unfortunately, increasing the party size almost always slows down the pace of the team substantially (like... easily doubling the time spent commuting to an objective). Longer trips means that teams are packing even more bulky items such as food and warm layers, and may face more serious risks for hypothermia and/or exhaustion.
As an aisde: readers from a climbing or mountaineering background may be wondering about other forms of protection-- such as pitons, chocks, etc.. While these tools have been used underground sporadically in the past and are occasionally in modern caving, they are not common enough to warrant discussion in this text.
Alpine rigging is when you install your bolts so the rope doesn't rub, allowing you to take a much thinner 8-10mm rope. Often, you will need an approach safety line to access the free-hanging rope. You won't always get a clean shot all the way down and may need to have some rebelays or deviations. It's not rocket science to figure out how to keep your rope from rubbing, but it definitely takes caving experience where alpine rigging exists to know how to properly bolt for zero rubbing.
ETHICS
Which one is better? Pull out the boxing gloves and let the forums explode. Bolts are impact, yes, but wrapping speleothems is also impact. Permanently drilling holes is changing the landscape but so are grooves cut into the rock from those "indestructible ropes" rubbing over them. Is a massive amount of webbing wrapping natural features and extending the anchor leaving less trace than two stainless bolts? You decide.
Try to find a balance between doing what everyone else is doing in your area and being a vigilante for a "better system". If no one knows how to use the bolts you've installed, or gets pissed and chops them, was your way better? Culture is one of the things to consider when installing bolts.
HORIZONTAL
Hand lines and lead lines need to be bolted well. You're not really putting force on it... until you are. The anchors can actually can see about 4x your weight if you were to slip and fall onto a horizontal line so take them serious. It's ideal to have 2 bolt anchors, a fully rated rope and for it to be installed chest high for an average person. If you have it at your feet, and then fall, doing a Factor 2 on a horizontal line... then you might be a highliner and we wouldn't want that.
REDUNDANCY
It's very common to have two bolts for an anchor but what about deviations and rebelays? Deviation with only a 20 degree change of direction is only going to see 1/3 of the force you put on going up or down the rope. Rebelays require a belly in the rope and therefore the anchors need better redundancy. Yea, it's "backed up" to the system above it, but if it blows and you drop 10 feet on a very static rope, especially while on tooth devices, you might die. If it would create a swing if the rebelay blew, then the shock load won't be as bad, but then you hit a wall or grind your rope to the core. Have redundancy when the consequences warrant it.
Metal
Caves are wet, including the "dry" ones, and many cheaper metals (like galvanized steel) do not like being in wet conditions. Moisture, be it actively flowing water or the humidity in the air, create perfect conditions to corrode non-stainless steel hardware (galvanized, zinc plated) alarmingly fast-- decades faster than if that same hardware was aboveground. Even worse is mixing metals, which leads to galvanic corrosion: a phenomenon in which different metals (including different grades of steel, such as plated versus stainless) that are in contact with each other and corrode. Galvanic corrosion is accelerated greatly by moisture in the environment.
Therefore, it is extremely important to use 316L stainless steel for the bolt, the washer, the nut and the quicklink!
Aluminum is light and carabiners are fine for short-term use, but it isn't a permanent solution and should not be left as permanent hardware underground. The aluminum oxidizes, especially where the anodized coatings has been scratched. See how bad these can look in our break test video of flaky and gooey carabiners . As an aside: titanium isn't necessary unless the hardware is exposed to salt, such as sea caves.
If you remember nothing else, remember this: Use 316L stainless steel for everything left permanently.
Yesterday's Bolts
Now let’s talk about hardware: it is common to see old and very ugly hardware in caves. The main rise of recreational caving started in the 1960s and self-drive bolts were the global standard. Even with the rise of gear manufacturers like Petzl, acquiring “real” climbing / caving / mountaineering gear was not necessarily easy in the United States (especially in rural areas east of California). As such, DIY hangers and hardware store anchors were common and plenty are still in many caves today (although we're trying to fix that).
You may be thinking: Wait, what the hell is a “self-drive” bolt?
The self-drive is a type of drop-in anchor that was designed for caving and seems to be a novelty aboveground. The galvanized anchor doubles as the drill bit and is embedded into the wall and held tight by an expansion cone that flares the flanges. It was the standard for bolting underground until the rise of the rotary hammer drills with lithium ion batteries in the early 2000’s. Lest we forget that operating a gas-powered rotary hammer drill in a confined space probably isn’t a good idea (...yes, there are some exceptions). As an aside: drop-ins and self-drives are anecdotally called "Spits," which was the name of a manufacturer back-in-the-day .
There are two main self-drives available today: new old stock Petzl Cheville Autoforeuse, and the extant Raumer Tap. There is a stainless steel anchor very similar to the self-drive, Raumer Rainox, which will be covered in the modern bolting section of this page.
Drop-ins, such as those at the hardware store, are the same as self-drives but the anchor lacks a built-in drill bit (hence it is simply dropped in, and not self driven). Until someone contacts me with a valid argument otherwise, I am firmly stating that there is no major benefit to the hardware store drop-ins versus a standard wedge or sleeve bolt.
Pros: self-drives
No power tools needed -- huge weight savings for extremely remote exploration (ex/ multi-day travel underground to frontier)
Anchors are cheap to purchase
Cons: self-drives
Self-drives aren't stainless, so they are not a good long term solution
Placement is shallow so the anchor is not as strong, nor does it handle shitty rock
Less room for error when installing them (including no tolerance for over drilled hole)
Requires practice to drill correctly, and a lot of practice to drill ''quickly" (<5 min./each)
Please don't use these unless you have thoroughly practiced placing them and know when it's appropriate to do so. If you are going to install them, know these details:
Delicate metals: remove hangers and machine screw upon derigging cave
Anchor: will rust over time; could galvanically corrode
Hangers: stock Petzl are aluminum, will corrode from cave environment
Low tolerance for crooked placements and uneven surfaces
Unideal pull on anchor weakens overall strength
Could cause hanger to spin, loosening the machine screw to the point of falling off
Drilled depth must be perfect: the back of the drilled hole is what pushes the cone into the bolt.
Too deep? The cone will not push into the flanges to engage the bolt
Too shallow? Anchor will not have full strength embedment
Clean hole imperative: cannot have rock flower (dust) preventing the anchor from engaging into the expansion cone.
When a cave is rebolted, we do not opt for 1-for-1 replacements. Rather, a completely new hole is drilled and a new bolt is placed in the vast majority of situations. There are reasons for this-- the primary being that we aren't rock climbing and thus the exact location of the bolt doesn't dramatically affect our experience. Additionally, removing old anchors (i.e. the "dropped in" part of the drop-in, or the stud of the wedge bolt) is simply tedious and unreliable...
Nobody likes bolt farms, so it is good to clean up the old junkshow when possible. Remove the old hangers by disassembling the anchor. If the hardware is stuck, try tapping (smacking it) back and forth with a hammer until it spins freely. If that doesn't work, keep hitting it with a hammer until something breaks. For wedge bolts that are totally rusted or seized, the easiest method is to snap the stud by using the socket end of the hammer and bending the bolt until it breaks. This has its limitations, but does work for a lot of shitty bolts. Cover up the scars of the old rotten hardware by hammering the remaining stud into the wall, then smearing it with mud.
If you are hellbent on actually removing an old bolt, see all the techniques for that in the Book of Pulling Out. The quick summary is that you have to attach a bolt remover, extract it, drill out the hole deeper and size it up and then install your new bolt. If it is so corroded you can't get the bolt remover on there, you can try core drilling around it or re-tapping the threads so you can screw the adapter on solid (but why even bother... just pick a new spot to drill).
Today's Bolts
A.K.A. what you need to buy if you are bolting a cave
[Sorry y'all, I'm working on getting this updated...]
It is becoming more common to mechanical bolts or even glue-ins. A 3/8" or 10mm bolt is super good enough since it's just static rope work, but length is what adds value in a softer rock like limestone (and especially rotting limestone). Broadly speaking, wedge bolts that are 3.5" / 90mm long (or longer) should be used. All the same concepts apply to installing these as you can read in the "Installing Mechanical Bolts" section of the Bolting Bible.
If you have the time to put glue-ins, they can be a great option in heavily trafficked caves. Just be sure to allow double the cure time for wet environments. If gluing overhead, be sure to use thicker glue. Hilti v3 500 will ooze even when 50F/10C but Liquid Roc 500 can almost be too thick to even squeeze it through the mixing nozzle when it's cold. A/C 100 is a good all around glue but it's not as good as epoxy, but super good enough.
Concrete screws are awesome, though not UIAA approved. A 3/8" x 4" Titen HD is crazy bomber. 7.5mm Multi Monte Screws are kinda good enough for temporary exploration. Read all the nuances in the Concrete Screw section of the Bolting Bible before using them.
Small Stuff
During vertical exploration, lead aid climbing, and general exploration where you don't know where you would want long term anchors, skinny stuff might be temporarily used. This could be a 7.5mm (5/16") Multi-Mont screw or wedge bolt. The screw could be upsized for a permanent anchor or the wedge bolt can be smashed in if you over drill the depth and covered with dirt. Since this is temporary, zinc plated is the best option. Some fancy cavers use the expensive removable 8mm Petzl Pulses and just reuse them over and over leaving nothing but a hole.
Good Examples of Pitch Head Rigging
Hangers & Connectors
While there are some very unique hangers specific to caving, the common plate hangers are used most regularly in modern times. Read all about those in the HANGER section of the Bolting Bible. For redundancy on the important issue, we'll say it again: use stainless quicklinks on stainless hangers on stainless bolts. Also, make sure the quicklink can open wide enough to get a rope in there.
Standard Hangers - This is the most common type of hanger across all sports and is also the go to for most cave bolting. It comes in 316SS, it's rated, you can fit two carabiners in it and it's super affordable enough. These can be pulled in tension or in shear.
Horizontal Hangers - Also called "wing" hangers. Keeps the carabiner perpendicular to the rock to keep your knot from rubbing. These are not meant to be pulled in tension (direct pull) because it levers on the bolt, so do not place these in a ceiling placement.
Mini Top by Raumer - A hanger had a baby with a quicklink. No connector needed because it opens! It still leaves plenty of room to connect yourself to the anchor. The problem is they only are made for 8mm bolts so if you wanted 10mm or 12mm bolts you can't use these. Funny they are rated to 25kN when 8mm bolts would rarely hold that much force.
Ring anchors - You can tie your rope directly into any hanger made with round stock. Dupla and Pingos are similar in that you can run a rope in them but keep in mind those only are made in 304 SS and don't come in 316L.
Dyneema cord "hangers" (and connector) - called AS - "Amarrage Souple" (soft anchor in french), these consist of an aluminum button with a dyneema cord loop integrated into it, creating an extremely lightweight anchor piece. These pre-made version are from ClimbingTechnology (CT), but it is simple to create a DIY version. A word of warning: they are not common in the US, so it might confuse people who are unfamiliar with them. Additionally, the hardware of the pre-made CT anchors is not stainless steel so it is not intended left installed underground.
Alien hangers - These are a niche 2 hole hanger designed for the Raumer stick up method of aid climbing, though you may see them floating around elsewhere. It only has an 8mm hole so it's not ideal for a permanent anchor,
Clown Hangers - Old styler of aluminum hanger used on self-drive ("spits"). The rope sits on the bolt and is hugged by the hanger. These are made of aluminum and meant for deep exploration where they will be removed afterwards. See them tested starting at 11:03 of our experimental Dyneema Cave Anchor video. Don't clip a carabiner to the Clowns!
Go Deep In Caving
This Bolting Cave section is not meant to be stand alone material, please go read the rest of the Bolting Bible. And another resource that is super helpful for a niche activity is Derek Bristol's channel, specifically his CAVE BOLTING PLAYLIST.
Sexy Cave Photos
Just to make caving look more fun than it really is. ETHAN REUTER takes amazing photos, be sure to check out his instagram!
What's Next?
You can always go back to the main part of the BOLTING BIBLE HERE
Feedback, typos or more information is always appreciated. HMU at ryan@slackline.com
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