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;

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.

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