When a lower mounting of the Versa-Mil unit is required, the compound rest can be removed and replaced with a special adapter base (Figure 5- 12) that mounts directly on the cross-slide. The base plates are semi-finished and may require drilling two mounting bolt holes and a pivot pin hole. The location of these holes depends upon the lathe model and size. The base plate adapter should be used for operations on or below the centerline of the workpiece. Such operations include milling keyways along the side of a shaft, surface milling with a shell end mill, and drilling or boring on the centerline of the workpiece. The compound rest must be removed prior to mounting the base plate adapter.