Workshop accuracy begins with a benchmark straight edge as a surface reference. These Canadian-made precision steel straight edges are ground flat over the entire length on both edges, the 300(12") and 610(24") lengths to within 0.025mm and the 915mm(36") length to within 0.038mm. All have been stress relieved to remain true under temperature variation. Useful for checking whether surfaces are flat or straight, they are 38mm wide and easily stand on edge unsupported, leaving both hands free for precise measurement or tool adjustment. All have hang holes, allowing storage on a nail or hook.A. 300mm(12") Steel Straight EdgeAt just over 500g and 6.3mm(1/4") thick, the 300mm straightedge is a handy size for checking things such as plane soles or water stones for flatness. It is also a good choice anywhere a larger straightedge would be unwieldy in use or would risk damaging the item being checked.B. 610mm(24") Steel Straight EdgeAn invaluable aid for machine set-up, the 610mm straightedge is a good size for setting up stationary machines such as planers and jointers. At slightly more than 1kg, it weighs enough to stay in place while you make adjustments. 6.3mm1/4" thick.C. 915mm(36") Steel Straight EdgeGreat for long-bed jointer and larger machine set-up, the 915mm straight edge is a good master shop reference. Weighing a substantial 2.6kg, it is 9.5mm(3/8") thick. The linished sides give a textured surface that makes the straight edge easier to grip with confidence.