Abstract: The invention provides a comb (10) which includes means for indicating to a holder of the comb when the comb is being held at a predetermined angle to a known datum plane. In a preferred form of the invention, the comb (10) includes, either fixed to it or integral with it, a scale marked (16) with angular graduations (24), and a pointer (31) which is biased so as to point in a specific direction at all times, alignment of the pointer with chosen graduation on the scale then ensuring that the comb is oriented at a desired angle to the datum plane. The pointer (31) may, for instance be biased gravitationally so as to point vertically irrespective of the inclination of the comb.