Abstract: A T-shaped instrument includes a first body portion having an edge that is adapted to slide along an edge of a sheet of material and a second body portion that has a plurality of slots that are oriented to be parallel to the edge of the first body portion. An instrument, which can be a marking instrument or a cutting instrument, is placed in at least one of the slots and will mark or cut the sheet as the instrument is drawn along the edge of the sheet. Roller bearings can be located in the first body portion and markings, such as numbers, can be located on the second body portion adjacent to the slots.