Ruler with safety shield

A tool for aiding marking or cutting is described. A V-shaped member having an edge formed at an exterior apex of the V for guiding a marker or cutting tool. The exterior surfaces of the V-shaped member may have a material applied having a higher coefficient of friction than that of the V-shaped member. The edge at the apex of the V may have two substantially planar surfaces, each of which forms a complimentary angle with the interior apex angle of the V, or a thin metal portion formed in the exterior apex of the V so that an edge thereof protrudes sloping towards a surface on which the tool is laid. A graduated scale may be applied to an exterior surface of the tool at a location near the apex.