For a center spike, carve a 2-inch-long sharp stick—or better yet, a sharp spike of bone—and lash it to the inside of the fork. Start with a clove hitch about a half inch below the fork, and wrap the windings tightly toward the fork. When the lashing reaches the fork, continue by making a few more wraps to create a pocket for the butt of the spike. Place the spike in this pocket, then continue lashing by alternating the cord under and over the spike, tightening with each lash. Secure the lashing.