A sling may be used when the urethra has dropped out of place or when the sphincter muscle of the urethra is weak. The sling is a narrow strap that is placed under the urethra. It acts as a hammock to lift or support the urethra and the neck of the bladder. There are different types of sling procedures. They differ in the type of material used for the sling, the type of incisions needed, and how the sling is placed.