On sinew and rawhide as lashing.

Sinew and rawhide, or babiche will expand when soaked in water. The soaked collagen can now be manipuated to tightly wrap objects like sticks or stretched futher to its material limmit in the case of a skin thong, or to wrap arrows. 

It's a common misconception that the wrap made from a sinew thread or rawhide thong will shrink and creat an extra tight wrap from that which was made in the soaked condition of the material. As the moisture leaves, the material will shrink, but not tighten and expiriance has shown that it becomes loose as the water which once occupied it leaves it to thin out.

Even the tightest wrapps I have made have become, at best, a sturdy bind, but not a tighter one.