The modern coupler (universal since 1870, required by law since 1880) is semi-automatic, train-activated, with a "knuckle" that closes around its counterpart much like a pair of hands shaking. A coupler is attached to each end of freight and passenger cars, and cabooses. The tender also has a coupler at its rear (or train) end, with the draft gear tucked inside the end sill.

Couplers "shake" hands like humans.

Ready to couple

Fully coupled