Head Bag

Mounting it is the whole point. The bag holds a head taken from a kill, and back at base it goes onto a small or large hunting trophy. Until then it does nothing but take a slot in your inventory.

You cannot craft one. It comes out of the hunt: drop an animal, harvest the whole body with a skinning knife in hand, and besides the meat and leather you walk off with the head. The other knives and the hatchet leave you without one.

The game's text talks about a defeated foe, and the trophy stands name enemies next to animals. So the roamer who sniped your farm all week might end up on your wall beside the bear, though nothing in the item data confirms that player heads work.

A bare skull goes into the skull trophy instead.