Abstract: Fastmark Groutline Ruler enables tile, stone and masonry installers to properly measure tile, stone or masonry materials which will be cut and installed between the end point and the previously installed materials on the floor or wall. This device is a two piece measuring device which will automatically deduct the size of the required grout-line(S) measurement from the fill cut, Fastmark Groutline Ruler has subtractive grout line stop block that automatically aligns to the edge of tile stone or masonry edges, even on crooked horizontal or vertical edges, removable subtractive grout line stop blocks can be mounted to standard hand held tape measure, stop blocks have a depth adapted to the depth of grout spacers installed in field area for perfect grout spacing, and subtractive grout line stop blocks that automatically subtracts for of grout line(S) sizes. Subtractive grout line stop blocks made to all grout line sizes and multiples of.