Fisting is a sexual activity that involves inserting a hand into the vagina or rectum. Typically, fisting does not involve forcing the clenched fist into the vagina or rectum. Instead, all five fingers are kept straight and held as close together as possible (forming a beak-like shape, casually referred to as a "silent duck"), then slowly inserted into a well-lubricated vagina or rectum. Once insertion is complete, the fingers either naturally clench into a fist or remain straight. In more vigorous forms of fisting, such as "punching," a fully clenched fist may be inserted and withdrawn slowly. Fistees who are more experienced may take two fists (double-fisting) in the vagina or rectum. In the case of double-fisting, pleasure is derived more from the stretching of the anus or vagina than from the thrusting (in-and-out) movement of hands.

The Silent Duck is the technique most often used, where the person engaging in hand insertion makes a beak-like shape with their hand resembling a duck. Double Fist/Side Prayer is a very advanced technique which only few are capable of achieving. The person engaging in hand insertion (the fister) places their hands palm to palm forming a position similar to one used when praying. Handler then turns theirs parallel to the floor, pointing fingers towards subject's vagina and/or anus.