Gaffs are undergarments worn by some members of the transgender community and cross-dressing performers. Gaffs are intended to comfortably hold male genitalia out of sight, allowing men and transgendered persons to wear tight pants, dresses, skirts and swimsuits with no visible bulge. Commercial gaffs can be quite expensive, but you can make your own with a pair of old pantyhose.
Cut one leg off the pantyhose and twist it to make a thin rope.
Hold the pantyhose rope around your waist and tie one free end in a simple knot around the other free end to make an adjustable knot. You have now made the waistband.
Cut off 10 inches of the other pantyhose leg, from the top of the thigh down, to make a tube. Treat the cut ends with clear nail polish or anti-fraying glue to prevent runs.
Slip the tube around the waistband so the tube rests in the center, where the crotch will be. The gaff is now ready to wear.