A coupling or coupler is a mechanism, typically located at each end of a rail vehicle, that connects them together to form a train. The equipment that connects the couplers to the vehicles is the draft gear or draw gear, which must absorb the stresses of the coupling and the acceleration of the train.
Scharfenberg coupler on a Southeastern Class 395
Three-link coupling on an antique tank wagon
UIC standard screw coupling, shown attached and tightened
A link-and-pin coupler
Janney couplers are a semi-automatic form of railway coupling that allow rail cars and locomotives to be securely linked together without rail workers having to get between the vehicles. They are also known as American, AAR, APT, ARA, MCB, knuckle, Buckeye, tightlock or Centre Buffer Couplers.
Syracuse Malleable Iron Works – 1894. MCB5 Transition Coupler, compatible with link and pin coupling
MCB Type 5 coupler circa 1893. Split knuckle accommodates link and pin coupler or Johnston coupler. Vertical hole in knuckle accommodates the pin. Could also have accommodated a buffers and chain coupler with an extra pin.
AAR Type F Interlock couplers, rigid version at right and rotary version at left. The one on the left lost its pin and was pulled out of its coupler pocket.
Mated Janney Type E couplers, as seen from above. Left is top-operated on locomotives. Right is bottom-operated on cars