Repair and maintenance of couplings, in particular automatic couplings for the mechanical engaging and disengaging of objects compelled in opposite directions, including cranes, pipes or pontoons, for forming a rigid connection, including for air, steam, water and power conduits between these objects; repair and maintenance of vehicles, in particular rail-mounted vehicles and superstructures therefor; repair and maintenance of apparatus for locomotion by land, air or water; repair and mainten...