This is one of our favorites from Core77's collection of Workshop Workhorse gifts: when it comes to production, precision begets precision. This high-quality machined doodad will multiply the uses of your trusty ruler, turning it into a capable production aid. Slide it on and start quickly squaring things up and marking consistent depths. When done break down and stow it.
Czeck Edge Ruler Stop
Available at Core77's Hand-Eye Supply