Maintenance of intact skin throughout the body is essential to prevent dehydration, to act as a barrier to infection, to allow unrestricted movement, and to provide a normal appearance. A flap is a piece of body tissue, usually skin and fat, that always has its own blood supply. Therefore, a flap can be moved anywhere it can reach without worrying about the circulation present at the place that needs it, which is called the recipient site. When compared with all other possible choices, a flap best meets all the requirements for any area needing skin replacement. The keystone type flap as one such option is so named because its design has the shape of the keystone of a Roman arch. If taken from loose tissues adjacent to a defect, it can be simply cut and advanced for any necessary skin coverage. Direct closure of the donor site where this flap comes from is possible so that usually a quite good overall cosmetic result is also obtained. These virtues are shown as an overview in this video where a keystone flap is transferred after removal of a common basal cell skin cancer from the lower lip.