A drill guide, of the type that has a main body with a flat base and an aperture for assisting the movement of a drill bit, interchangeable drilling heads for guiding drill bits of different diameters, the heads designed to be optionally attached and fit onto the housing defined according to the size of through hole of the main body that has the aforementioned interchangeable drilling heads and inside apertures of different diameters on each drilling head, the apertures are specifically designed to guide drill bits of different diameters, a positioning device for attaching the drilling head in use in a set position inside the housing, and a retaining device for retaining any of the interchangeable drilling heads inside the housing.