The flap can be taken from either lip, but it is most commonly switched from the lower to the upper lip (3, 4, 5). Its shape has been varied in form from triangular to rectangular to square to even more odd and irregular configurations. The shape and size of the flap depend, of course, on the defect to which the flap is to be transposed, bearing in mind that it need not necessarily be the exact size of the apparent defect. When the flap is taken out of one lip to be inserted into the other, the donor lip is reduced. This may lessen the amount needed for the opposite lip if normal lip proportions are to be maintained.