A Lead flange is an external or internal rib, or rim, for strength, as the flange of an iron beam or I-beam; or for a guide, as the flange of a train wheel; or for attachment to another object, as the flange on the end of a pipe, steam cylinder, etc. Thus a flanged rail is a rail with a flange on one side to keep wheels, etc., from running off. The term “flange” is also used for a kind of tool used to form flanges.

A flange can also be a plate or ring to form a rim at the end of a pipe when fastened to the pipe (for example, a closet flange). A blind flange is a plate for covering or closing the end of a pipe. A flange joint is a joint, as that of pipes, where the connecting pieces have flanges by which the parts are bolted together.