Headpointing is the process of toproping a route into submission prior to leading. This can be an excellent technique for a beginning level leader that is worried about taking a fall. However, it is far more often used by high end climbers that wish to ascend something that is incredibly run-out.
In Great Britain, there is an entire culture of climbing on gritstone, a compact stone with few cracks and an ethic that doesn't allow for bolting. This is where headpointing was first developed as a technique to "safely" climb hard and exposed lines. But, just because you rehearsed the route over and over again, that doesn't mean that you won't fall and hit the deck. As Neil Gresham says, "unless the will to do the route surpasses all, you shouldn't be there..." Headpointing is just one tool, but if it doesn't work out, the consequences could be severe.
In this video, Neil talks about "the black art of headpointing" while demonstrating his use of it on a dangerous 5.12+ gritstone climb. This is definitely one of those climbing videos where your hands are going to sweat...
--Jason D. Martin