Know Your Meat Cuts - Beef Sirloin?
Beef Sirloin is a large section of the carcass that runs from the 13th rib all the way back to the hip bone and from the backbone clear down to the flank (or belly).
The full sirloin is itself subdivided into top sirloin and bottom sirloin. Top sirloin is generally fabricated into steaks that are good for grilling.
After separating it from the top sirloin, the bottom sirloin is usually divided into three main components: the tri-tip, ball tip, and flap, which do well with roasting and barbecuing (and they are sometimes made into ground beef).
The back end of the tenderloin, called the butt tender, is also situated within the sirloin, and it's either removed altogether when fabricating a whole tenderloin, or the back end is used as a roast.