Try this description, best I can find but will post back a diagram if I can find it again
Definition: This one steak brings more questions than any other. Originally a California cut, this steak (and roast) has become increasingly popular because of the superior flavor and because it is a steak built for grilling. The tri-tip steak is cut from the tri-tip roast. The tri-tip roast is a triangular section of the sirloin primal and comes from the point where the sirloin meets the round and flank primals (tell your butcher this if he doesn't know what a tri-tip is).
above found on
http://bbq.about.com/od/steakglossary/g/tri_tip_steak.htmHey Al, if you don't mind saying how much do you pay for your small orders of Tri-tip?