shown in fig1 and 3 is achieved when the door 18 alone or in unison with door 17 is to be moved laterally outwardly of the door opening to an open position the power arrangement for moving the door requires the operator to turn the hand wheel 52 which rotates the drive pulley 54 in turn occasioning the winding of the cable on the guide pulley and idler pulleys to move the door laterally placing tension on one side of the cable and providing a slack on the other side of the cable the movement of the cable thus is conventional in the prior art in response to the rotation of a suitable wheel and drive wheel arrangement in the present instance the advantages of the invention are achieved in that the drive pulley is of a high friction type having been constructed of high friction polyurethane whereas the low friction guide pulley is constructed of a material known as polyethylene the guide wheel structure of the present invention thus in combination with the drive pulley provides for maximum contact between the cable and the surface of the drive pulley by eliminating the possibility of the cable climbing on itself since the magnitude of the frictional engagement force between the drive pulley and the cable is related to the extent of the pulley surface contacted by the cable this feature provides for an improved and more efficient cable driving.