Yevamot 102 - A shoe used for Chalitzah
Chalitzah is the procedure required to release a widow from her connection to her late husband's brothers and to permit her to marry anyone she wants, rather than one of the brothers (which marriage would be called "yibum").
Chalitzah requires five people: three to act as judges and two - to make the fact well-known. The Kohanim then will know not to marry her, and other people, by contrast, will know that she is available.
Part of the procedure is for her to remove his shoe. The shoe should be proper, made from leather, and fit to be worn. As an enhancement, they add a strap to the shoe, so that that the two actions - untying the strap, and the removing the shoe - leave no doubt in the validity of the procedure.
Rabbi Yannai asked, "What if she tore the shoe of his foot, or burned it off his foot? Do we need the foot to become exposed - and that is achieved - or do we need proper removal?" - To this there was no answer.
Art: The New Shoe by Elizabeth Nourse