The tenderloin is an oblong shape spanning two primal cuts: the short loin and the sirloin. The tenderloin sits beneath the ribs, next to the backbone. It has two ends: the butt and the tail. The smaller, pointed end – the tail – starts a little past the ribs, growing in thickness until it ends in the sirloin, which is closer to the butt of the cow. This muscle does very little work, so it is the tenderest part of the beef. The tenderloin can be cut for either roasts or steaks.