Home » Tip of The Day » The Units & Ruler SettingsThe Units & Ruler Settings June 9, 2016. Posted in: Tip Of The Day. Double-click on the ruler (Ctrl R / Command R) on the left side or top of your canvas to bring up the Units & Ruler settings dialogue box. « Previous Photoshop Tip: | Next Photoshop Tip: » Sign-up for the PTC Newsletter so that you'll never miss a tutorial!. Your Email Address: