Make sure that the back up does not defeat the function of the original piece of equipment. For example, backing up a healthy tree that is more than 12 inches in diameter may not be effective. Best construction materials are plastic or fiberglass. They should be adjustable and have chin straps. Everyone in the rappelling areas must wear a helmet.
Leather gloves are the best.
Nylon gloves will melt and cloth gloves tend to wear out quickly. Brake hand must be gloved. Long Pants and long sleeved shirts provide protection. Sturdy footwear is required. Tie glasses with strap.