Tape Measure Tool - Creating A Guideline a Precise Distance from Starting Point

Quick Tip if you use an extended keyboard, as I do, when inputting a precise measurement from a starting point to create a guideline. Recently I was unable to input my intended distance. I discovered, with some excellent and friendly guidance from Dave R, that I had inadvertently hit the keyboard button Num Lock, thereby turning the number keys off. Result: no guideline anywhere! Be sure your number pad is on!