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Bolting For Caving

It’s fun to play in tight wet holes, but use the proper protection!

The Bolting Bible

Bolting For Caving

Welcome to our free course as our way of contributing to the bolting 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. Also, if someone is going to spend their time and money to bolt something, I assume, 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. Get it?

Our courses are A-Z content in blog format, glued together with an overarching blog we call a textbook. A blog format is easy to read, easy to update, and easy to translate. Be sure to begin at the TEXTBOOK and at the end of each episode we'll point you to the next.


A huge thanks to RACHEL for contributing so much information and so much old-bolt porn to this section Also, thank you John Fioroni of Cave Exploration Society /, as well as Big Name Pit Bouncer Ethan Reuter for your contributions.


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 hurt fragile ecosystems, break beautiful features, or just leave a footprint. So please think before installing a bolt. Also, consider the bolts can actually help preserve an area by providing a dedicate route for ropework and thus avoiding unintentionally smashing speleothems, or dislodging loose rocks from the walls. Think holistically about your impact.


Are you allowed to bolt??? Who owns or manages that cave? If it is a new cave discovery, who will be managing that cave and what will they say when they do? Know your area first before installing permanent hardware in it.

If you are replacing bolts, who installed the original bolt? Will they be throwing a fit that you are changing it? Do the cave owners/managers gate keep (get it?) the process or want to at least give input? Know your area 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 way 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, etc, or it could be a total hellscape with death-flakes peeling off!

Don't Wallow In The Mud

Mud life!

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

Caves often follow faults, joints, or fractures in the bedrock. Therefore, it isn't surprising that the rock creating the cave passage or a pit can be chossy, full of shale, or structurally compromised from geological activity. Even in the same cave or the same wall, it is common to see bands of different quality rock, and some layers may be more sound than others.

Sandstone - Avoid it

Underground sandstone is sketchy because it is totally saturated by moisture. Cave sandstone does not have the baking-hot sun to dry it out or has ever had weathering to exfoliate it's pores (get it?). When selecting a bolt placement, cave sandstone should be approached with caution if not avoided all together.

Large slab of chert (black) surrounded by clean-washed grey limestone

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. It can form on practically any surface, too. It may be anchored to a really bomber foundation of bedrock, or it may 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.

Imagine installing a screw in a phone book instead of a block of wood. The bolt placements in speleothems are sketchy because of how it's layered. If there is a solid wall behind the flowstone coating, and there are no other options, then just make sure the bolt is actually installed in the solid rock behind it. Keep in mind that damaging cave formations can have serious legal repercussions, plus it is just an asshole thing to do!

A bolt is only as good as the rock in which it is placed.


The vast majority of limestone caves are wet. In the eastern United States, it is very common to see streams underground as well as waterfalls plunging through the cave. Unsurprisingly, these water conditions can vary by season and weather and some caves even flood. Dry caves are often the result of water abandoning that passage (or even the entire cave); this is called a paleo or fossil passage. That said, most caves are constantly humid (>90% humidity) and the air does not “dry out.” Moisture, be it actively flowing water or humidity in the air, create perfect conditions to corrode non-stainless steel hardware (galvanized, zinc plated) alarmingly fast. These bolts can rust decades faster underground than if that same hardware was aboveground. It is extremely important to use 316L stainless steel for the bolt, the washer, the nut and the quicklink! Titanium isn't necessary unless you are near the ocean and the hardware is exposed to salt.

Aluminum is light and carabiners are fine for short-term use, but it isn't a permanent solution. The aluminum oxidizes, especially where the anodized coatings has been scratched. Aluminum carabiners should not be left as permanent hardware underground. See how bad these can look in our break test video of flaky and gooey carabiners:

If you remember nothing else, remember this: Use 316L stainless steel for everything left permanently.


Check out our tools section of the Bolting Bible for everything you might need but here are some cave specific tips. Everything, like usual, should have a tether in case you drop a tool. Most drills can handle some water but if mud is covering all the vents, the drill could over heat. Your drill may not last very long if you are taking it in caves but you can keep it in a dry bag until you need to pull it out to give it a fighting chance. If your space is confined and you are trying to squeeze glue into the hole, you can add a flexible straw to keep the epoxy gun at a 90 degree angle to the hole. The longer that straw is, the more glue you are wasting.

It is absolutely imperative to use a hammer to test the rock before bolting because voids can exist without being visible. Piton hammers are fairly oversized for caves, and lighter bolting hammers are recommended. Raumer's Action hammer or Petzl's TamTam has a socket in the end to screw on nuts for 8mm bolts and adapters are available for 10mm.

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.


IRT 11mm vs 9mm for alpine rigging. Rig so ropes don't rub if possible.

Where do you put the holes and therefore the bolts? If you anchor to natural features or bolt where it is easy to set up for rappel, your rope is likely going to rub the edge as you go down and come back up. IRT means Indestructible Rope Technique and requires a big ass 11mm pit rope that feels as stiff as cable but ironically isn't indestructible and still requires padding. Bigger gear is harder to carry or requires more people to be in a team, both of which can drastically slow you down. There is always a time and place this could make sense to have an anchor where a bomber rope rubs an edge with padding, but there is definitely a better option.

See how a 40 year old Pit Rope held up

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.