If you have the compulsion, like I do, of stepping on every cellar door in Manhattan, it may not be a case of OCD. If these surfaces invite stepping--or at least reduce the chance of slipping--thank diamond plate (not the church) for preventing your fall. Embossed into steel or aluminum surfaces, diamond plate is a "tread," the upward-facing counterpart of a sneaker or tire surface. These elongated diamonds (rhombuses really) criss-cross at right angles, creating more diamonds (squares actually) in the negative space.
