Use caution in pounding the sinew. I actually use an old carving mallet (basically a cylinder of dense wood) and an flattened egg shaped smooth rock. If you use a hammer (steel), or too much force in your pounding, you can actually sever the fibers and waste a lot of material and time.
Sinew is used for nock and point reinforcement and fletching support on arrows; it can and is also used to reinforce suspect areas on a bow. Sinew, when applied to the back of a bow can induce a reflex or hold the shape of a heat bent bow. I have recently sinewed a California type bow and tied a clothes line from nock to nock in reverse bend. I put a rat tail file handle through the center of the rope and twisted to impart more reflex as the sinew cured. I would call this a primitive 'Perry' reflex. I also used sinew to wrap the 'break' nocks at the end. I use sinew exclusively now on my arrow fletching since other man made threads are brittle and have broken on many occasions during use. Sinew is the only material that stands up to being bounced off a rock, tree or whatever...it's one tough customer. I typically cover sinew (after it's completely cured) with rawhide or snakeskin to improve water resistance. I cover that with melted paraffin wax for a finish and clean everything up with pledge after a days shoot. Sinew is tough, requires time and patience to work, lasts a long-long time and is completely natural...what more could anyone ask for?
