A coupling (or a coupler) is a mechanism typically placed at each end of a railway vehicle that connects them together to form a train. A variety of coupler types have been developed over the course of railway history. The design of these couplings is almost as important as the railway gauge since flexibility and convenience are maximized if the couplings can work together no matter what order they come in.

• Semi-permanent and Automatic couplers
• Damper & Collapsing tube
• Support for the gangway
• Air connection