US Patent 4,355,801
United States Patent and Trademark Office
University of Iowa Research Foundation (Iowa City, IA, US)
An adjustable ankle strap for holding weights used in leg lifting exercises. The device "includes" of a single continuous strap having an adjustable fastener at its ends, the strap extending in a cross pattern through a loop affixed to a cushion that rests on top of the foot. The single strap provides a double loop, one of which fits beneath the arch of the foot with the other extending around the ankle with the cushion resting on top of the foot. A fastener is provided on the strap for attaching the desired weights.
Thomsen, Timothy A. Adjustable weight lifting holding device for leg lifting exercises. US Patent 4,355,801 filed December 09, 1980 and issued October 26, 1982. https://ir.uiowa.edu/patents/31