Abstract: A pair of spaced-apart, parallel rings is provided, with each ring provided with a plurality of semicircular loop portions pivotally connected to the respective ring about its circumference. Each ring has two sets of a plurality of semicircular loops, a first outer set that is pivotal in a first direction away from the other ring, and a second inner set that is pivotally connected to the first set of loops of the other ring. The loops of each set are arranged in an overlapping manner, so that when one of the loops is rotated, all of the loops of that set are concurrently rotated. Since the inner sets of loops of the two rings are pivotally interconnected, rotation of any loop of either of the two second inner sets will concurrently rotate the other loops of the second inner sets. Rotation of these loops of the second inner sets is achieved by drawing closer the two rings or by pulling them apart. The two first outer sets of loops are free to rotate in either direction.