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Bolting Bible - Book of Holes

Drilling holes to install climbing bolts

The Bolting Bible

The Book of Holes

“After getting thy hole hammered, make sure thou cleanest it really well.”

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 over arching blog we call a text book. 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.

Holes matter a “whole” lot! You have to know where to put them, what pattern to put them in, how to drill them and what diameter they need to be, even sometimes accurate to within 0.1mm. And did you know that if holes for glue ins aren’t super clean, they could fail at a dangerously low forces? Keep in mind drilling a hole is a permanent deformation to the rock, so be intentional before you swiss cheese our public land. See here all the things you need to know to get your holes drilled out.


HIGHLINE Bolt Placement

Things to consider before installing highline anchors:

1. Where do you want your master point to be? It will be the center of your bolting pattern so choose carefully. And remember you don’t want more than a 45 degree angle on your anchor legs so it doesn’t put exponential force on the bolts, instead sharing the load evenly.

2. Is the anchor going to serve more than 1 highline? How can the bolts be placed to best be pulled in multiple angles?

3. Will the hangers sit flat against the rock?

4. Will there be a weird hump between the bolts and the master point causing unwanted friction?

5. How far back from the edge will the bolts be?

A. In hard rock it can be a foot or two away from edge but if it is too close then it can put the master point too far beyond the edge making rigging difficult.

B. In soft rock it is important to stay away from the edge even 6 to 10 feet back in some cases but then the master point will need extending possibly requiring a stabilizer bolt, one near the edge that doesn’t hold much force other than to keep things from moving around causing abrasion.

6. What Pattern will you use?

A. Straight line - Careful, this is how they harvest quarry stone. This can score rock and make it susceptible to fracturing. Know your rock. STRAIGHT LINE PATTERNS DON’T EQUALIZE on top of cliffs but being pulled straight out of a cliff wall may equalize better.

B. Equilateral Triangles equalize best if on top of a cliff. The bolt most direct in line (the center bolt) and the closest bolt sees the most force. Those two principles cancel each other out for the most part if you do an equilateral triangle, with the center bolt being furthest back. Learn more about directional relativity here.

Example of how the force is spread within the rock

7. How close, or far, should the bolts be apart from each other? The force is spread at a 45 degree angle through the rock.. You can see an example in this photo of a piece of sandstone that broke while pulling a short mechanical bolt straight out in a bolt buster test. If your bolts are too close together, the same sections of rock will be seeing forces from two different bolts. It’s also important to not be too close to areas of the rock that sound hollow or weak when tapped with a hammer. The longer your bolt, the bigger your cone will be, so the further your spacing will need to be. The expansion anchor industry has established a minimum of 10 anchor diameters apart from each other (½” x 10 = 5” or 12mm x 10 =120mm apart minimum) and is talked about in this video and in engineering the standard is 12x diameter. Either way, I’m not sure why diameter has much to do with it when it looks like length affects cone shape more. For most climbing situations, since we use either ⅜” (10mm ish) or ½” (12mm ish), a hand width apart is fine but in softer or fractured rock it is better to spread them out twice as far. Also, this includes edges as you can see in this video how a bolt too close to an edge is unsafe. Whether length or girth is more important, stay 5” or 125mm away from any other bolt or edge or hollow sounding rock and you’ll be bomber.

8. How many bolts will you use? In highlining, we made a sport taking factor 2 falls on death triangles with ropes that don’t have sheaths, so it was common for people to put in 4 or 5 bolts on either side. After BoltBuster research, we found out that bolts are pretty awesome if your rock is awesome. Therefore, 2 bolts are redundant, 3 is now common for highline anchors, and 4 bolts are just overkill as it is difficult to equalize them. Only 2 or three bolts ever see the force anyways. Just make sure you have quality bolts in quality rock.

9. What are the regional trends and is it correct? Don’t do anything drastically different than others have done in the area without fully understanding why they did it.

CLIMBING Bolt Placements

Check out two of our most popular bolting videos showing two ways to do this. Top down or bottom up.

1. To avoid rock failure, place bolts an appropriate distance from rock edges, further in softer rocks.

2. Avoid placements that weaken your carabiner by loading it over edges or rock imperfections.

3. Plan placements to avoid rope drag. Keep bolts on a sport route in line to avoid the friction of the rope redirecting back and forth across the route.

4. Avoid placing anchor bolts too far from the cliff edge, forcing the rope to rub.

5. When bolting sport routes, find good clipping stances, then make sure to place the bolt so most climbers will be able to reach it. If you are really tall don’t place it as high as you can. Place the bolt so a shorter climber will be able to comfortably use the same stance to clip the bolt. As a tall climber try placing bolts that you can reach with your elbow or nose from a secure position.

6. Consider when a quickdraw is hung on the bolt that is won’t be in the way of a key hand or foot hold as you climb past.

7. Place top anchors so they protect as much of the route as possible. If the route wanders, place the anchor in the middle of the zone that the route traverses to prevent big swings on top rope.

8. Hitting the ground, wall and/or a ledge is bad. Bolts should be placed to avoid this.

A. Spacing: Remember that your ground fall potential resets at every ledge. Space your bolts accordingly. The closer you are to a ground fall the closer your bolt spacing should be. It sucks to get injured when nothing fails.

B. Position: Consider what happens if you were to fall clipping the next bolt. In addition to ground/ledge falls look out for swinging falls or falls that will slam you into a wall.

9. When putting in anchors for a climb that will only/mostly be top roped, consider the safety of those walking to the cliff edge to set up the climb.


Believe it or not, bolting companies are not lining up to sponsor us; mostly because there is no money in such a niche industry. $1 per episode helps a ton and so does grabbing MERCH if something grabs your eye. Lots of designs and options.

Drilling Basics

Here are some pointers for drilling holes regardless if you are hand drilling or power drilling.

1. Drill the hole deep enough.

In almost every situation, there is no such thing as too deep, other than you are wasting battery life/arm power, drill bit life or glue. IT IS VERY BAD IF THE HOLE IS TOO SHALLOW. Just like relationships, if it is too shallow it isn’t going to last. A bolt sticking up out of the rock could be unsafe and difficult to remove. Even at 95% depth it will look like it is in the rock but the hanger will be spinning and that always raises

a red flag on the integrity of the bolt to someone who wants to use it.

TIP: Put duct tape on your drill bit or your wire brush as an indicator that you are deep enough. Lightly scoring your drill bit with a hacksaw blade works as well and doesn’t fall off or move.

2. Drill it straight.

A. Mechanical bolts will have a hanger and it is important that the hanger sits flat against the rock.

B. Glue in bolts have conflicting information online. FixeHardware says in this video to tilt them backwards for leverage. Bolt-Products website (scroll halfway down) did a test showing stakes in the ground do better if installed straight in. I believe glue in bolts act much like ice screws where the threads are supposed to do the work, not the leverage. Ice screws are recommended to be tilted 10 to 15 degrees towards the direction of pull so it doesn’t leverage the top of the ice but allows all the threads to be pulled on. So just drill glue ins straight in for soft rock and let the entire shaft and glue do the holding rather than the angle.

Ice is fragile, ice screws are installed in the direction of pull. Let the glue do the holding, not the leverage.

3. Test the spot

A. Set the hanger (if using hangers) where you think you will drill the hole to make sure it sits flat and nice. If you really like the spot and only a few crystals are stopping you, you can chip them away with a hammer, but just be sure that the end product… the hanger… will sit nicely.

B. After drilling the hole an ⅛”, stop and check everything again. Do you like the spot? Does your hanger sit nicely? Did the rock feel/sound solid? If you goof, ⅛” isn’t a deal breaker, but if you drill all the way and then realize there was a mistake, then it is just slop.

4. Bring Backups

A. It really sucks if you don’t have a backup drill/batteries or backup bit or backup glue tip or even backup hardware in case you miss counted or dropped one and you can’t finish bolting. The impact that bolts have on an area has been debated, but everyone agrees a half drilled or half installed bolt is bullshit.

5. Drill Bits

A. A 4-point bit drills faster and saves energy or batteries rather than 2-point bit. They also make a rounder hole which is required for some bolts such as the pricey but sexy Petzl Coeur Pulse removable bolts.

B. Fresh bits are important because the tip/shoulders get worn down on old bits and you get an undersized hole. If the hole is too small, then you have to smash your mechanical bolt in harder which can damage it or the glue in will not have as much glue surrounding the rod. c. Battery powered hammer drills and Petzl Rocpec hand drills require SDS-Plus drill bits, “special direct system”. This type has the groves at the top so the drill can hammer and rotate the bit. Not all SDS bits are created equal. SDS-Plus is 10mm shank and SDS-Max is 18mm. So make sure you know what you are buying. d. Size matters - the usable length and overall length are generally different by 2” because of the shank, or the part that goes into the drill. Remember that a 6” drill bit only has 4” that is usable.

It helps to understand all 5 parts:

i. Shank: has two sets of grooves so the bit doesn’t fall out and helps during


ii. Land - raised portion of the spiral (similar to the crest or peak of a wave).

iii. Flute - the spiral groove which facilitates the removal of the concrete dust as the

hole is being drilled.

iv. Head and Tip - these work together to break up the concrete. The carbide is brazed

onto the head to harden the tip of the SDS bit to assist in the breaking of the concrete.

Hand drilling

There are some places that do not allow power tools, such as National Parks in the USA. However, if it is legal and ethical to install bolts, you can do it the ol’ fashion way… by hand! Functions the same as rotary hammer drills. Except you provide the hit with a hammer and the turn with your wrist instead of a battery doing all the work.

1. You need a handle. The poor man’s method is wrap duct tape around the shank until comfortable but the efficient way is to use a Petzl Rocpec, designed for SDS drill bits or the high quality D/5 Hurricane Drill which is designed for both SDS and HSS bits. If you want to learn how bad this sucks for only $27 you can buy a SDS max to SDS plus adapter because the max shank is huge and easy to hang onto.

2. You need a hammer… obviously. You can use any 12oz construction hammer but the Yosemite Hammer ha