Suitable for: all 1/4 or 3/8 drill bits, perfect for horizontal, straight or inclined drilling, drilling on the edge of a board or on round material The guide rails themselves feature springs for quick return when drilling repeatedly Depth stop and large handle: adjustable depth stop and control of the head spring action. The drill adapter slides onto the guide rails, whether on the wall, ceiling, at an angle or in round materials, precise drilling is easy Angled positions are possible 45 degrees, and rubber pads in the base hold the guide in place to allow drilling of round materials up to 45 degrees in diameter. 3 inches