Slotted ruler

A slotted ruler comprising a ruler left end, a ruler right end, a ruler length extending from the ruler left end to the ruler right end, a ruler top, a ruler bottom, a ruler width extending from the ruler top to the ruler bottom and generally perpendicular to the ruler length, a ruler rear surface configured to rest on a substrate, a ruler front surface opposite the ruler rear surface, a ruler thickness extending from the ruler front surface to the ruler rear surface and generally perpendicular to the ruler length and ruler width, a straight longitudinal slot having a slot left end located to the right of the ruler left end, a slot right end located to the left of the ruler right end, a slot length extending from the slot left end to the slot right end and generally parallel to the ruler length, the longitudinal slot having a slot top, a slot bottom, a slot width extending from the slot top to the slot bottom and generally parallel to the ruler width and a slot thickness extending from the ruler front surface to the ruler rear surface, wherein the slotted ruler is comprised of a transparent or translucent material, wherein the slot width is between about 0.001 and about 1.0 inches, wherein the slot length and ruler length are between about 4 inches and about 25 inches, wherein the slot length is less than the ruler length, and further wherein the slotted ruler further comprises a first set of widthwise hatch marks extending generally parallel to the ruler width, adjacent to the ruler top, and spaced at regular intervals along the ruler length, a second set of widthwise hatch marks extending generally parallel to the ruler width, adjacent to the ruler bottom, and spaced at regular intervals along the ruler length, and a first set of regularly ordered numerical indicia spaced at regular intervals along the ruler length, and

• further wherein the slotted ruler further comprises a first set of widthwise lines generally perpendicular to the ruler length and a first set of lengthwise lines generally parallel to the ruler length, the first set of widthwise lines and the first set of lengthwise lines forming at least one lengthwise row and at least ten widthwise columns of adjoining large rectangles located on one side of the longitudinal slot, wherein the slotted ruler comprises a second set of widthwise lines generally perpendicular to the ruler length and a second set of lengthwise lines generally parallel to the ruler length, the second set of widthwise lines and the second set of lengthwise lines forming at least four lengthwise rows and at least twenty widthwise columns of adjoining squares located on an opposite side of the longitudinal slot, as compared to the adjoining large rectangles, wherein the adjoining large rectangles have a width generally parallel to the ruler width and a length generally parallel to the ruler length, wherein the adjoining squares have a width parallel to the ruler width and a length parallel to the ruler length, wherein the slotted ruler comprises more adjoining squares than adjoining large rectangles, wherein the median length of the adjoining large rectangles exceeds the median width of the adjoining squares, and further wherein the median surface area of the adjoining large rectangles is larger than the median surface area of each adjoining square, and further wherein at least some the first and second set of widthwise lines are aligned with at least some of each of the widthwise hatch marks adjacent to the ruler top and ruler bottom.