Chop! Chop! Send!
Climbing a hand or finger crack well is about as close as you’ll ever get to performing magic as a climber. When non-climbers see it, they’re just stunned. How can a person go right up that wall using nothing more than that little crack!
The idea is that you use your hands and feet to mechanically lock your limbs to the crack. For a hand crack, imagine you’re standing next to the crack doing that cute little Miss America wave with your hand. Find a spot that a bit wider than your hand and slot it in. Thumbs up sometimes, other times thumbs down, depending on the situation.
Once it’s in there, fish it around, forward and back, up and down a bit until you find a nice constriction to wiggle it into. The way you make it wedge tight is by rolling your thumb inward you palm to make your hand fatter across the profile. This expansion is what’ll allow you lock your hand in there like it’s caught in a vice.
For upward progress, you do the same thing with the other hand. And you manage to twist your toes and jam them into parts of the crack kind of the same way. Then you push/pull up with three limbs while you remove and reposition your low hand and foot to a higher spot.
Lather, rinse, and repeat as necessary.
Now you know what Jimmy Hendrix was talking about in Voodoo Chile when he sang, “standing next to a mountain. . . chop it down with the edge of my hand.” He could climb 5.13 cracks, you know.