The hinged jaws are used to grip around the shaft of the nail so it can be pulled out. The jaws will usually be drop-forged and attached to a box joint, to give them extra strength and precision. The box joint means that one of the jaws passes through the other, this interlocking joint keeps each part steadier than a standard pinned joint.
The side of the jaw attached to the shaft, or shank, of the tool is dug under the nail head; then the jaw attached to the pivot point is engaged to lock the jaws closed around the nail.
Handle of a nail puller
The handle of these nail pullers is used as an integral hammer or rammer. It forces the jaws down and around the head of the nail, even if the head is flush or slightly below the surface. The handle moves up and down on the shaft so there is no need for a separate hammer to be used.
The advantage of having the hammer built in to this tool is that there is no need for a separate claw hammer and with some practice it can sometimes be operated with just one hand. However, the handle does make the tool heavier and longer so it is more awkward to carry and store.
Pivot point of a nail puller
The pivot point, or fulcrum, is often called the base heel or foot piece. This is used to close the jaws around the nail and then lever the tool over to pull the nail out.