I’m a strong proponent of hangboarding for increasing finger strength for rock climbing. I’ve tried many different methods, and IME, hangboarding is the most effective. For basic instructions on how to go about hangboarding, check out “The Making of a Rockprodigy”, a training plan my brother Mike & I developed many years ago. I get a lot of questions about the specifics of hangboarding, and it seems like many of the same questions come up over and over, so here is a series of Frequently Asked Questions about the subject, in no particular order.
First, review Hangboarding FAQ #1, as these topics are related. Next, consider the concept of “Specificity”. This is a fundamental concept of all forms of training, and it basically means your training should be as similar as possible to what you are training for. In the context of this question, that means you need to determine the type & size of holds you will be climbing on when you are at your limit. If you primarily climb at a single crag, this should be fairly simple, as hold types and sizes tend to be fairly consistent at a single crag, with difficulty varying with other factors such as length, steepness, or hold orientation & spacing.
If you travel a lot, and visit many different types of crags, this can be difficult to nail down. The typical hold on a 5.12 at Rifle is much different than a 5.12 at Smith Rock. Everybody needs to train edges, but maybe you are particularly keen on pocket routes or big slopers. Pinches are very common at overseas limestone crags but not so common in the US. In this case, consider which types of routes really inspire you, or are more important to you, or represent a more limiting weakness for you. Perhaps you have a “big hairy goal” route in mind. What are the holds like on this route? Even for those who travel extensively, you probably have a favorite crag or type of route, the type of route that you typically select when you’re looking for a next-level project. Use that type of route as your guide.
To maintain specificity, select hangboard grips that best replicate the size & shape of these “limit holds”. Ideally these holds should be a bit of a stretch for you when you’re starting out. If you typically climb 5.12, I recommend hold sizes more typical of the 5.13s at your favorite crag, since you will be progressing quickly through the grades now that you’re training. If you’re an enduro jug-haul fiend, its likely your holds will be relatively large, so expect to add lots of weight while hangboarding, or use one-arm hangs. In my experience it gets pretty dicey once you’re adding 75lbs. or more. If you are set on this type of climbing, you may consider doing more than the standard number of reps and/or sets as another way to increase resistance without adding dangerous amounts of weight.
For thin face climging afficianados, the selected holds will probably make it necessary to remove weight. This is easier than it sounds, but be sure to use a repeatable, quantifiable method for doing so. Popular methods include hanging from elastic bands, putting your feet on a chair, or getting a power spot from a partner. These methods all suck, so top using them! Go to Home Depot and get two cheap pulleys, or get some fancy climbing-rated pulleys here. Install two (or more) eye bolts below your hangboard, attach the pulleys to the bolts and run a cord through the pulleys. Clip one end of the rope to your harness and the other end to however-much weight you want to remove, and voila! you just lost 40 lbs as far as your fingers are concerned.
Once you’ve identified the right type & size of holds, plan to stick with them for several seasons (so you can gauge your progress from season to season), but also be prepared to down-size as you improve. If all goes well, eventually you will find yourself crushing grips that once seemed unreasonably small, so be on the lookout for the appropriate-sized holds once you attain that next level.