Narrowing of the chin leaves a bony step on each side of the chin-mandible junction, and this discontinuity should be diminished to reduce its palpability and for a smooth jaw line. Additional lateral incisions are made alongside the previous intraoral incision that was made for the chin narrowing procedure. These incisions are separated from each other because exposing the mental nerve increases the incidence of direct nerve injury during the operation. Subperiosteal dissection is then performed through the newly made lateral incisions to obtain direct visual access medially from the chin-mandible junction and laterally to the mandible angle. The use of a “guarded” oscillating saw to mark the proposed osteotomy line is recommended (Fig. 10.3) [10, 14]. This guarded saw has a small oscillating saw that is shielded at various distances. The size of the guarded saw to use is determined by the size of the bony step (which correlates with the amount of chin narrowing) and the distance between the lower mandible border and route of the nerve. The saw allows the surgeon to perform a precise bone resection in a uniformed manner while avoiding over-resection and reducing the possibilities of nerve injury. The extent of the ostectomy should be extended to a point posteriorly to allow a smooth jaw line. This point can be in the middle of the mandible body or just anterior to the gonion, depending on the shape of the mandible, the steepness of the mandible plane, and the amount of chin narrowing. If the posterior extent of the resection is too short, an unnatural and unsmooth jaw line, namely, a “secondary angle,” may form, resulting in an unaesthetic outcome [10]. After the osteotomy line is marked with the guarded saw, larger oscillating saws are serially used to complete the bone resection. Additional mandibular corticectomy can be performed if further narrowing of the width of the mandible body is required (Fig. 10.4).