An implement for orientating a tool at a predetermined angle with respect to a plane of a target surface to be engaged by the tool, particularly for orientating a surgical cutting tool perpendicularly to bone tissue for harvesting and implanting a bone plug to repair damaged bone tissue, includes a rod having a distal end coupled to a head formed with three contact points arranged in a circular array around the longitudinal axis of the rod, such that the three contact points define a plane. The rod is coupled to the head with the longitudinal axis of the rod at the predetermined angle to the plane defined by the three contact points, such that when the three contact points of the rod are in contact with the target surface, the longitudinal axis of the rod is at the predetermined angle with respect to the plane of the target surface.