Abstract: The low side of a well bore drilled by a rotary drill string with a drill bit thereon is instrumentally determined as to direction and inclination. An eccentric tubular member is rotatably supported on the drill string and is provided with projection means extending beyond the drill bit diameter and lowered into the well bore. The eccentric tubular member rotates so that the heavy side thereof rests on the low side of the well bore and positions the projection thereon in a predetermined circumferentially spaced and angular relationship relative to the low side of the well bore so that the projection engages the well bore wall during drilling operations and urges the bit laterally of the well bore.During drilling operations, the projection means assumes authority over the drill bit since it extends beyond the diameter of the drilling bit and thus positions the drilling bit laterally in the well bore in a predetermined manner as the drill string is rotated to drill the well bore.