From The American Rifleman archives: Terminology: Topstrap by Wiley Clapp - Friday, March 19, 2010 This term applies to revolvers and is used to describe the bridge of metal running along the top of the main frame from the vicinity of the rear sight forward to the threaded portion of the frame that accepts the barrel. On early revolvers of the cap-and-ball era, a top strap was frequently omitted as superfluous. Indeed the first big cartridge Colt revolver—the so-called Open Top of 1872—had no topstrap. But they found that a stronger design with a topstrap was necessary for the more powerful cartridges of the 1873 Peacemaker. It is a virtual fixture on modern revolvers and I can't think of a single model from any maker that does not include a top strap.