The humble cam hook is an essential modern aid climbing tool for moving quickly in crack systems that are generally too narrow for spring loaded cams; i.e., slightly smaller than Donald Trump's pinky finger.
Instead of fiddling with a micro stopper or (gasp!) banging in a piton, just slot a cam hook vertically into that micro crack, carefully step onto it, and it magically locks itself into place. The first few times you won't quite believe that it actually is going to hold, but your trust and confidence will grow quickly.
Repeat as needed by alternating your aiders, and when the runout starts getting spooky, then put in solid gear. (That little stopper you place with a gentle tug for fall protection will be a lot easier for your second to clean than one you have bounce tested with your full weight.)
It's best not to bounce test cam hook placements if you’re doing several in a row. Just ease onto the upper placement with a firm step into the aider, and move up.
You want to buy at least two cam hooks, one for each aider. Fortunately they are quite inexpensive. MountainTools is a fine place to score some. They come in four sizes, with the middle two generally being the most useful. Pictured below is I think the Leeper medium, which has worked well for me.
Note that cam hooks are generally not used in soft rock like sandstone, because the force they can generate can literally break the rock. The smaller size hook, the more force is generated. Apparently the newer cam hooks made by Moses have a model called “fragile flake” that’s acceptable for use in softer rock, but I haven’t used them.
The typical way to deploy cam hooks is to have them on a short loop of webbing, and clip them to the top of your aiders when you need to use it. (Like this; a perfect placement in my wooden deck!) Yes, that webbing loop could be about 2 inches shorter, but we’ll get to that in a moment.
However, here’s an alternate set up - if you anticipate a lot of cam hooking, you can girth hitch the hook directly to the top loop of your aider. like this:
This offers a few benefits.
You can deploy your hook fast; no reaching for gear on your harness
You get a few extra inches of reach on the placement, because there’s no carabiner involved
You can never drop the hook
You could tie the hook directly into the top of your aider. However, this makes the hook pretty much permanently attached to the aider, because the water knot connecting the webbing is going to get welded. Aid climbing is confusing and clustered enough without adding anything unnecessary into the equation, so in climbing where you don’t need the hook, it’s cleaner and tidier NOT to have it always on the business end of your aider.
With a girth hitch, the cam hook is ready to use fast when you need it, but is easily removed when you don't.
To rig this, get 18 inches of 1/2 inch webbing for each hook (or 3 feet for 2 hooks). Yes, this looks like a lot of webbing, and you may have an inch or so left over, but those darn water knots always seem to take more webbing and than you think.
Tie a water knot through the cam hole to make a loop, that's a half inch or so longer than the length of the cam. You’ll probably have to experiment a couple of times to get this loop just the right size. If the loop is too big, you lose reach on every placement. If the loop is too small, you won't be able to girth hitch it.
Water knots are notorious for loosening under repeated cycling loads, so tighten down the knot with a pair of pliers, and check it often to be sure it's not loosening up.
The original and classic cam hooks were made by Ed Leeper, so they are sometimes referred to as Leeper hooks. They are now manufactured by Moses, and available through various outdoor retailers, such as MountainTools.
Here’s a nice video that shows the basics of using cam hooks.