Meat
Flat/Flap Cuts
Butcher's steak: See Hanger.
Flank: From lower/back belly. Marbled (but leaner than Flat Iron) and tough. Usually sliced thinly against the grain. Common cut for jerkey.
AKA: Bavette (French), Stir-fry beef.
Flat Iron: From chuck / upper shoulder to neck. Marbled, tough, and flavorful. Usually sliced thinly against the grain. Has a membrane that is usually removed.
Hanger: From diaphragm. Very lean and tender. Most tender cut aside from tenderloin. Has a membrane that is usually removed.
AKA: Butcher's Steak, Flap (incorrect labeling), Skirt (in Brittan), Onglet (French)
Skirt: From upper/front belly. Adjacent to Hanger. Marbled, tough, and flavorful. Usually sliced thinly against the grain. Looser structure. Covered in a membrane that is removed before cooking.