LD wheel, wheel group, drum group, hook group, pulleys, couplings, wire rope, cable pulley, motor, brake, reducer, cable reel, overload limiter, standard parts.

The four corners of the frame are provided with four pulleys. Wire ropes pass round the pulleys and are tightened on the reel drum of a crane trolley.

The screen reel drum and the card-shelf reel drum are fixed above the blackboard, and the picture clip is fixed on the upper frame of the blackboard;