A sheath is very similar to a contraceptive condom. It fits over the penis and collects urine into a connected drainage bag.
Finding the correct size and fit is the most important part of successful use. Usually two piece sheaths or adhesive sheaths are used.
Two piece sheaths have separate adhesive strips that you apply first. Adhesive sheaths have glue on the inside and are rolled onto the length of the penis and warmed with the hand slightly to encourage adhesion.