Bone carver is the skill related to the processing of bones, skulls, and other non-food animal products.
In fortress mode, bone carvers make bone, shell, ivory/tooth, horn and pearl goods at a craftsdwarf's workshop. These include bone bolts for crossbows, lightweight bone and shell armor, and totems from skulls. Bone carvers can also decorate furniture and goods with these materials.
Your adventurer can practice bone carving without a workshop simply by standing over a pile of bone, pressing x to open the crafting menu, choosing "Carve Bone", and selecting an item to produce. This process requires you to be holding an edged tool or weapon. Only jewelry, figurines, and cut bone "gems" can be produced this way, none of which have any major use except for trading (or, more obviously, training misc. object user). However, doing so does train agility, spatial sense, and kinesthetic sense, all of which are useful combat attributes.