An improved locking pin (10) for locking together two pieces of equipment (12, 14) through aligned locking apertures (16, 18). The pin comprises a steel casing (20), a steel insert (22) and an elastomer member (24). The two steel parts assemble together in a particular sequence and are adjusted so that when completely assembled, the insert (22) is locked into the casing (20) with the body of the casing (20) and the insert (22) being parallel and spaced from one another. The elastomer member (24) is interposed in the space defined between the casing and insert, and fills the space between the steel parts. The assembled steel parts are firmly locked together by introduction of the elastomer member (24) into that the space. There is no adhesive joining the steel and elastomer members which makes the pin more amenable for use in corrosive environments and also eases manufacture of the pin components. A tightly constructed locking pin also avoids the problems of the components becoming loose or lost.