Once the drawing is complete, an incision is made on the marked line perpen­dicular to the skin with no undermining of the flap, to limit interruption of the blood supply to the flap. This must be done with some care. Distally, beyond the external opening of the fistula, the cutting is not perpendicular but angled away from the flap, again to preserve as much blood supply as possible. If electrocautery is used during the dissection, only low power is used. As the circumferential mobilization con­tinues, the flap will spontaneously start to migrate into the anal canal, becoming less horizontal and more vertical in its orientation, that is, it will “stand up” (Fig. 1b). At the proximal margin, the border must be freed a bit from the internal sphincter but without undermining. The internal fistula opening is then excised. The deeper internal opening can then be closed, usually with only one or two interrupted sutures of absorbable material. The flap fully mobilized will seem to have shrunk a bit. When performing the anastomosis of the proximal flap to the rectal mucosa and internal sphincter, it is important to spread it to the lateral margins of the initial internal incision. Interrupted absorbable sutures are then made, full thickness in the flap and to internal sphincter and mucosa proximal to the internal opening closure. Usually only four to six stitches are needed, and the line is examined for gaps when complete. No sutures are placed on the lateral margins or posterior or distal margin of the flap for three reasons. The first is in order not to diminish the blood supply to the flap through injury or compression of the blood vessels in the island. The second is that sutures in the anoderm hurt. The third is to avoid any outward tension on the flap.