This video is about the coupling process between a locomotive and the railway coaches in Sri Lankan Railway. The best place to watch that process in Sri Lanka for passengers is the wooden observation coach of Calypso special train which is running between Badulla - Bandarawela - Demodara. I got these clips while forming the train for the evening turn at Demodara Railway station.
In here, SLR used CBC couplers for coupling process because class M6 diesel electric locomotive has that method of coupling. It is the common types of couplers in Sri Lankan Railway 🇱🇰. But there are some other couplers in SLR like Screw couplers.