A flange is an external or internal rib, or rim (lip), for strength, as the flange of an iron beam or Ibeam (or a T-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, or on the lens mount of a camera. 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 .

All types of flanges are available for high end industrial requirements. Conforming to different quality standards, flanges are engineered in metals like stainless steel, cabon steel, inconel, monel, nickel, titanium, dulex steel, etc. and standards like DIN, ANSI, BS, JIS.