Sounding or urethral sounding is the medical use of probes called sounds to increase the inner diameter of the urethra and to locate obstructions in it. Sounds are also used to stretch the urethra in order to receive piercing. Urethral sounding and urethral play are also used to refer to this practice in a sexual context. Urethral play can involve the introduction of either soft or rigid items into the meatus of the penis (as well as farther in). Objects such as sounds are usually only inserted about halfway into the glans and can usually be easily retrieved. Other toys and items, such as catheters, may be introduced deeper; in some cases even into the bladder. Some items may even be allowed to curl several times or expand within the bladder. This action in the male may be directly or indirectly associated with stimulation of the prostate gland and some types of bladder control.