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Safety is your responsibility. This article is not a substitute for qualified in-person training.

This article will give you some basic knowledge about bolts in the US. We encourage you to learn more about climbing bolts in the areas where you climb.


Though land management agencies such as the National Park Service do have rules and, in some cases, permit systems to regulate where and how many bolts are installed by climbers, in most cases they do NOT monitor the installation process, nor do they check whether existing bolts are safe. This responsibility lies with the climbing community.

Whether you are top-roping, leading, or rappelling, a bolt failure can have catastrophic consequences. Don’t assume bolts are good.


1. Route History

Because most of the bolt is hidden in the rock, learning about the history of the route will give you the first clues. A guidebook is a good place to start—most guidebooks have historical information about climbing development in the area, which will give you an idea of when and how the bolting was done. Was the crag developed with a super pure old-school ethic, all bolts hand-drilled on lead and only when there was a stance, never hanging from a hook, so the routes tend to be run-out and scary? Was the entire crag safely bolted by a passionate crew of local climbers who regularly check all the bolts and also do trail work and clean the outhouse (and is there a tip jar at the local gear shop?). Online resources often contain route history and may include updates on recent rebolting efforts. Talking to other climbers can also be a great way to learn about area history and ethics.

2. Basic Knowledge

What climbers call a “bolt” is usually either a mechanical anchor bolt plus a hanger or a glued-in one-piece bolt.

2.1. Mechanical Anchor Bolts

Mechanical anchor bolts used for bolting routes are often repurposed concrete hardware from the construction industry. Some rock climbing companies also make mechanical anchor bolts.

We find two main types of mechanical anchor bolts in the rocks: split shafts (aka compression bolts) and expansion bolts.

Split shaft anchors are forced into the hole with a hammer. Some have a round head, while others have a thread and a nut. The dangerous 1/4-inch Rawl Drive was the go-to piece of hardware for American climbers in the 60s and 70s. A lot of them have been replaced already, but there are still many out there. The 5/16-inch and 3/8-inch diameter ones may be fine if they are in good granite. In softer rock, like sandstone, split shaft anchors are not safe.

There are two main types of expansion bolts: sleeve and wedge. Sleeve bolts are often preferred because some are removable, and they will be easier to replace when the time comes. The shank diameter is key: 1/4-inch is considered unsafe, 3/8-inch is often considered a minimum and 1/2-inch is preferred.

Unfortunately, once a bolt is placed in the rock, there is no way of telling what kind or how long it is. An inexperienced route-setter may have placed a bolt that’s the wrong kind or way too short. Again, knowing the history of the route will help.

2.2. Hangers

Nowadays, most first ascensionists use hangers that are specifically made for rock climbing. Seeing the brand name of a climbing company and a high kN rating are often signs of a good hanger (but not of a good bolt or solid placement).

A few decades ago, rock climbing hangers were not as widespread, and the bolting knowledge was not as good as it is today. On less popular routes, you may still find SMC “Death Hangers,” recalled Leeper hangers, aluminum hangers (manufactured or homemade), etc.

You should be very suspicious about a hanger that:
1) doesn’t have the general shape of a modern rock climbing hanger (looks too thin, has geometric angles instead of all curves)
2) doesn’t appear to be made of rust-resistant steel (shows rust), and
3) seems to be made of aluminum (aluminum is not strong enough for hangers)

2.3. Glue-in Bolts

Glue-in bolts work better than mechanical anchor bolts in soft rock. There are many types and shapes of glue-in bolts.

Installing glue-in bolts requires specific knowledge. For example, a hole that was not perfectly cleaned, the wrong type of glue, or a badly mixed glue could make for a very weak bolt.

2.4. Placement

The strongest bolt and hanger can be dangerous if they are in poor rock or were badly installed:

A bolt may pull out if the rock is too soft to hold a certain type of anchor.

The hole may be too big in diameter or, too short for the bolt to be strongly held in place.

A piece of the rock where the bolt is may detach itself.

If the angle of pull is close to the bolt angle, it is relying less on shear strength and more on tension strength, which is usually much weaker.

3. Inspection

A bolt that looks perfect from the outside may have been poorly placed, may be a wrong type, may be way too short, or may be rusted behind the hanger. Once in the rock, there is no way to know for sure that a bolt is “bomber.” However, there are many clues to look out for:


  • Is it a split shaft? If yes, is it in anything other than good granite? (A rounded head is probably a split shaft, but a split shaft may have a nut)
  • Is the diameter too thin? (3/8-inch is considered the minimum by many these days)
  • The visible part of the bolt has rust (the part in the rock is probably much worse)
  • The nut is not tight (you may try to tighten it with a wrench, but do NOT overtighten as you may weaken it)
  • The shank/shaft is crooked
  • Keep an ear/eye out for 5/16-inch button heads and 3/8-inch split shafts which have a tendency to snap
  • etc.


  • Not the classic rock climbing hanger shape (e.g. recalled Leeper hanger, homemade hanger, hanger with low rating)
  • Rust (e.g. old SMC “Death Hanger,” recalled Leeper hanger)
  • Made of aluminum (e.g. homemade hanger, hanger with low rating)
  • It has a crack line
  • etc.

Glue-in bolt:

  • Prying the bolt parallel to the rock with a carabiner makes the bolt move inside the hole (you feel an actual shift, and not just bending of the hardware)
  • Heavy usage has made a noticeable groove in the metal


  • Bad rock (e.g. soft rock, hollow sounding, flake, too close to an edge or a crack)
  • Bad hole (e.g. too wide, not deep enough)
  • Bad angle of pull (e.g. angle of pull is close to the bolt angle, relying on tension strength instead of shear strength)
  • The hanger is spinning
  • etc.


Bolting and rebolting should not be taken lightly. Unless you are willing to dedicate a lot of time and are willing to listen and learn from others, you should leave it to people who are truly experienced. Many mistakes can be made, such as using mixed metals or choosing poor placements. Bolt-related accidents can be tragic and cause climbers to lose access to climbing areas. If you are willing to dedicate a lot of time to rebolting, reach out to a local team or a national organization such as the American Safe Climbing Association (ASCA).

Always consider the environmental impact. Is it worth placing bolts in that location? Will this route be really used in the future? Never place bolts where traditional gear can be used.

If a permit is required, don’t skip that step—you don’t want to negatively affect the relationship between climbers and land managers, and possibly lose access to the area.


If you climb outdoors, you’ll likely clip an anchor that was replaced by climbers who were donating their time and expertise to make everyone safer. We suggest donating money and/or time to your local rebolting team if there is one, or to an organization such as the ASCA.

The ASCA is a nonprofit organization that replaces unsafe bolts and encourages good practices, such as painting new bolts to match the rock, reducing visual impact. Through its network of dedicated volunteers, it has replaced more than 20,000 bolts in the US over the past 20 years. Its website has a lot of information about bolts and the rebolting effort.

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