Abstract: Fifth wheel coupling apparatus including a trailer receiving plate mountable on a vehicle chassis and defining a receiving slot for accepting a trailer pin, a pin locking mechanism mounted onto the plate and comprising a generally stationary portion and a moving portion which is configured for sliding engagement with the trailer pin, the moving portion comprising a first sliding element which defines an inclined surface and a second sliding element arranged for engagement with the inclined surface at a first location therealong during locking engagement with a trailer pin and at a second location therealong when not in locking engagement therewith. The second sliding element engages a significant portion of the circumference of the trailer pin when in a locking engagement.