Hand jamming in climbing
Jamming is used where the rock features a crack in which you can jam your hand, fist, finger or in some cases forearm, rather than pulling down on a hold. In most cases you don’t actually pull down on a jam, it is used to stabilise the upper body as you push up from your legs.
Hand jamming can be done thumb facing up or down. The aim is to make the jam as secure as possible. Place your hand in the crack then draw you fingers in and tuck your thumb in. This will increase the volume of your hand in the crack, creating more pressure and a more secure jam.
Fist jamming relies quite heavily on the crack that you want to jam being slightly narrower than the width of your fist. Place your hand into the crack then make a fist, squeezing to make the jam secure.
Finger jamming works best when there is a constriction in the crack you want to jam. Choose the correct finger for the width of the crack (usually the index or middle finger), once placed, bend your finger to make it wider and more tightly jammed. Be very careful with this technique. If your feet slip and your finger is well jammed, you will almost certainly dislocate your finger at the very least!