Section 5 - The Book of Anatomy
"Know what thy is shoving in thou hole."
Some bolts have 5 separate parts and others are just a single rod bent and twisted into shape. Some are welded and some have hangers built into them. Surprisingly, for being just a metal “stick” you shove into a hole, there is a lot of details that go into them as they are basically tiny machines. Know how your little machine works so you know that it will get installed correctly.
Chapter 1 - Types of bolts
Let’s just skip over compression bolts (old school button heads). They are cheap crap that are barely worth using as a temporary anchor. I’ve never seen a highline anchor with button heads and I hope I never do. There are 2 types of mechanical bolts (bolts with moving parts), wedge and sleeve, and there are some sleeve anchors that are removable. Then there are bolts with no moving parts that are glued into the hole, cleverly named “glue-in” bolts.
Mechanical Bolts with Wedges
These bolts have a small expansion clip with bumps on the side located near the base of a bolt shaft. Those bumps don’t allow it to move since it is slightly bigger than the hole diameter. The very end of the bolt is cone shaped, so when the nut is tightened, it pulls the tapered end of the shaft up, expanding the clip. This kind of bolt is recommended only in hard to medium rock as the contact point is very minimal. Sometimes, this bolt gets extracted so much while wrenching it tight, mostly if the clip were to slip, that the threaded rod ends up sticking up so high that it hinders carabiners from clipping the hangers and leaves significantly less bolt in the rock. Never use these in sandstone or other soft rock as it can wear down the rock at the contact points under cyclic loads (whippers).
Mechanical Bolts with Sleeves
These bolts are threaded rods with a coned nut on the end. These are called sleeve anchors because the sleeve part covers the entire bolt shaft. The hex head and the shaft are one piece, rather than threads at the top with a nut. The “nut” is instead at the bottom and is coned shape so the tighter it is, the more it expands the sleeve. Therefore the hex head stays flush on the hanger rather than the rod sticking out. The sleeve also allows for more contact area and is ok to use for all types of rock although the softer the rock is, the more glue in bolts are preferred. These bolts especially need to be tightened at a specific torque, so if you don’t take a torque wrench with you, practice at home to get the right feel for it before doing your project. See the buying guide on for all your options at the end of the “Mechanical Bolts” section.
Removable bolts are great where you don’t want to leave permanent bolts because it is a high traffic area or it’s a highline that rarely will be rigged. It’s also great if you don’t want to wait for glue in bolts to cure, because these allow you to install the glue ins AFTER you highline on the removables. The concepts are the same as wedge and sleeve bolts, however the harder you pull on those bolts, the more they grab the rock. Contrarily, removables are designed so the sleeves can be pulled up separately after untightening, allowing you to avoid the wedging action that keeps the bolt in the rock. These should not be used as a long term anchor because if they ever were to loosen, they will not be safe to use. Just like all bolts, there are some downsides. They need to be drilled perfect because if it is to big, it just spins in the hole and if it is too small then it’s a real bitch trying to remove them. If a hole is repeatedly used for a removable, mostly in softer rock, it can wear out the hole, and no one likes a hole that is worn out! If someone tries to repeat a line, they may not know if it was a 12mm or ½” hole and that’s important because they require different bolts. Or the hole can get filled in with debris and need extensive cleaning. Also, in my experience, removables can look pretty mangled after a few “removings” so that’s why they aren’t called “reusable bolts” but “removable bolts”. They can be reused but not indefinitely.
Fixe’s Triplex (12mm) has a threaded rod with a tapered cone and Climbtech Legacy bolt (½”) is a flush hex bolt with a coned nut on the end. I have found Climbtech to be easier to remove than the Triplex. Climbtech, for good or bad, has a built in hanger rated for 25kn (also making them more expensive) whereas Triplex can use any 12mm or ½” hanger giving you more options. See Chapter 5 below for “Hangers”.
If you are real experimental and rich, you can try Climbtech's fancy removable anchor but I personally wouldn’t highline on them because the flexible wire would probably be kinked after a highline session and they are only rated for 12kn. If you use 8 of these for a highline, it should only cost over $600!!!
Petzl now has the Coeur-Pulse a 12mm removable that doesn’t require tools (assuming you already have a clean hole waiting for you). Those also are expensive but they can be used for highlining and are pretty fancy. They have an thin sleeve layer that gets pulled out of the way when you pull the trigger… aka… tooless. The fat heads on them limit how much you can clip to them but I do recommend them if you can afford them. A video on installing them can be found here.
And now for my favorite... glue-ins! A bolt that doesn’t need a hanger that people can steal, lasts longer than just your interest in highlining, and they can have static rope directly threaded through them eliminating 8 heavy quicklinks or steel carabiners. However, if you install threaded rod (stainless steel please), then you will need a hanger. But if you will be using an anchor for more than one highline and therefore will be pulled in more than one direction this is a good solution. This allows the nut to be loosened and the hanger turned. However, if hangers are removed and replaced often, the threads can get damaged making that bolt worthless. Glue-ins can come as a single shaft with a welded eye on top or a continue rod. U-shape glue ins require 2 holes (one for each leg) which is more impact for an area and isn’t used for any highlines that I’m aware of. It’s important the glue gets mixed right (since it is a 2 part epoxy that is mixed on the spot) and that the hole is 100% dust free, but it can offer some of the strongest anchors available.
Mechanical bolts are just pushing on a fraction of the sides of a hole but glue-ins grab 100% of the hole and that is especially important in softer rock or layered rock. The glue gets into the pores of the rock and makes for a bomber anchor compared to a wedge. It also keeps water out of the hole. They are much more technical to install and cost quite a bit more than a $9 mechanical bolt if the cost of the glue is counted, but they will last a lifetime therefore leaving less of a long term impact. You can buy them at Titan , Fixe , Wave or Petzl.
No glue-in is perfect. TITAN has a great titanium bolt that will last a very long time and is 35kn but you have to drill a 14mm hole, so this can only be used in areas you can power drill. This bolt gets hammered in lightly so it doesn’t risk falling out of its placement if installed in overhanging rock. FIXE doesn’t sell Marine Grade stainless in a 12mm diameter and 10mm isn’t recommended for highlines but their 304 stainless 12mm bolts are rated for 35kn. Also, the weld point is a potential point of failure and is really susceptible to SCC (Stress Corrosion Cracking). PETZL’S 14mm glue-in is 50kn strong but that’s huge requiring a 16mm hole. And their 10mm is too small for highlining, they don’t sell 12mm. Both of Petzl’s glue in’s are marine grade 316 stainless.
Do not use glue with mechanical bolts. You don’t get the best of both worlds, you get the worst. The glue will only sit on the outer sleeve and not attach to the actual rod that holds the hanger down. The glue could prevent the anchors from expanding. If the hole is big enough for glue, the wedge won’t wedge. If the hole is the right size for the hole, there is no room for the glue. The glue can also clog the threads. I’m not saying that a mechanical bolt is going to fall out of the hole easily if you use glue, but that is not how they are designed. Don’t try to get fancy!
Chapter 2 - Girth Matters
Bolts used for highlining see a lot more force than the ones used for climbing. ⅜” (10mm) isn’t sufficient. 12mm or ½” is the minimum standard bolt diameter for highline anchors. If bolting in softer rock or reusing a ½” hole for mechanical bolts then drilling a larger hole is recommended so this 5/8 SS sleeve bolt can be used.
Drill bits are important to get right. Although ½” = 12.7mm, you CANNOT interchange 12mm and ½” drill bits if you use removables. Sometimes 12mm and half inch bits can be interchanged for wedge or sleeve. And 12mm or ½” bits are fine for glue ins that require either one.
Chapter 3 - Length Matters
Your length depends on how hard you are… I mean, how hard the rock is. The harder the rock, the harder the hole, so don’t worry about deep penetration. 3” is fine for hard rock but 4” is preferred. The softer the rock the softer the hole and so you want to get it in as deep as you can. 6” is important for softer rock.
Remember, bolt lengths describe the entire bolt so keep in mind how much will be below and above the surface. It doesn’t matter how long you think it is but how deep it actually penetrates!
Chapter 4 - Washers
Washers distribute the pressure over more of the hanger (serious rocket science material here!). They might not be fancy but they are important. Some bolts, like Powers 5 piece rawl, comes with the washer. They are also very important if chain links are used instead of hangers (which is not an ideal method).
The most common mistake when using washers is to buy the shiny cheap ones at the store. Don’t use zinc washers! Stainless and stainless need to be together or that washer will rust quickly.
Chapter 5 - Hangers
We aren't talking about the airplane kind or the closet kind, but climbing hangers… and they are not all created equal.
The bolt holes generally come in ⅜”, 10mm, ½”, 12mm and CMI makes a rare hanger with a ⅝” (16mm). It’s important to use the right size bolt with right size hanger, otherwise it floats around the bolt and can twerk it wrong. And we shouldn’t be twerking around our holes!
The hanger strengths vary on normal size hangers around 25kn but Fixe's stainless ½” and 12mm hangers are 30kn certified with a 44kn ultimate breaking strength. CMI’s ⅝ hanger is also rated at a whopping 44kn.
The materials that hangers are made of also vary. I don’t know why aluminum hangers exist, but they do. They are not as strong and it mixes metals. Fixe sells PS (plated steel) and saves very little money in exchange for strength (about 10kn less) and longevity (don’t use zinc plated anything!). As amazing as the large CMI’s hangers are, they are just powder coated plated steel so that really kills the stoke I have for them. Stainless steel hangers are the only kind of materials that should be used for hangers. Fixe and Petzl both sell 304 stainless hangers. Fixe even sells a 316 stainless hanger.
Bolt-Products makes a 12mm (the size of the bolt hole) hanger out of 8mm stainless rod so rope can be threaded through, eliminating the need for quicklinks. The downside is that it is welded, increasing the risk of SCC (stress crack corrosion), and the weld point is a risk point of failure (though unlikely). They are rated for 25kn and a great solution to be able to run the rope directly in the hanger, which you cannot do with a normal hanger.
Chainlinks are commonly used as a cheap “hanger” that a rope can be threaded in and is generally rated for 30kn to 70kn. One downside is that they rust because no one buys high quality chain links. The other problem is they don’t sit flush with the rock, meaning they pull on the bolt about a half inch above the rock, creating a lever that greatly reduces the strength of the bolt. Also, if you see chains, there is a 90% chance there is a zinc plated bolt in the rock since price was the obvious deciding factor when installing the anchor. Consider the more links you have, the more points of failure you risk. These chain link bolts can only be used to pull shear (sideways) and cannot be used to pull a bolt in tension (straight out). You can buy SS chain in short length at RapBolting.