A brisket or tendon is normally paired with daikon instead of sinew. The sinew is actually a tough tissue in between the muscles. It is often sliced off and discarded when we cook the beef to prevent any chewiness. It is tough and chewy. However, with the right cooking method, it will turn springy and soft, with just the right resistance for a good chew, jut like a tendon would. I prefer to use sinew as it is often the cheapest as it is considered discards. This is just a way you can turn unused parts into something yummy.