Sounding rods can refer to two different things: a tool used to measure the depth of water in a ships hold, or a sex toy used in urethral sounding. Urethral sounding involves inserting a long, thin rod made of metal or glass into the urethral opening for sexual pleasure. The practice is not exclusive to penis-owners, but the technique is different for people with vaginas. Medical experts also use sterile metal or plastic dilators in the urethra for urological surgery to remove a retained foreign body within the urethra and bladder. However, there are high risks of injury associated with the practice of urethral sounding, including tearing or puncturing the tissue in the urethra, which can cause permanent damage.