What maintenance is necessary on trailers?

You answered correctly. On trailers, it is necessary to lubricate moving parts involved in the coupling and towing process, such as the fifth wheel and the towing fork. This ensures smooth movement, reduces wear, and prevents mechanical failure. Brake pads should never be lubricated, as they must have friction to be effective – lubrication would impair braking ability and create a hazard. So, for similar questions, only lubricate the coupling components, not the braking surfaces.