The flat iron is named for its distinctive shape, which looks a bit like an antique iron with its handle missing. This unique portion of the chuck shoulder clod is unusually tender and marbled.
The flat iron has a thick layer of very tough silver skin that runs through the middle, bisecting the muscle in half. Because of this silverskin, the flat iron is unusable whole. It cannot be braised or slow roasted, but instead must have the meat cut away from the membrane.