Friction wheel 1 rotates about fixed axis A and its flange a slides between link 2 and shoe 3 whose surfaces form a circular slot. When link 2 is turned clockwise with handle 4, link 2 and shoe 3 slide over flange a, but when handle 4 is turned in the opposite direction, link 2 and shoe 3 grip flange a and all the links move together with wheel 1 as a solid unit.
$2726$RG,ML$