First, hitting shift immediately snaps the measuring rectangle to the nearest visible edge (like the border of a button or window). Second, once you’ve measured something, you can copy the values as CSS or Objective-C code, and directly paste them into your text file. And third, you can easily resize your selection rectangle by single pixels using the arrow keys (something I have to do often when I’m working with a trackpad).
Both xScope and SnapRuler are really nifty, and get along nicely with each other.
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