Screen Divider

From Iconico:

You can't hold a measurement device like a ruler or protractor up to a computer display and expect it to be accurate. That's why Screen Divider was developed - to give you a reliable way to measure distances, Cobb angles, and confirm parallel lines, for any image or schematic that's on your computer screen. Screen Divider directly addresses an ongoing problem facing all designers that work with digital renderings - how to quickly and effectively conduct length, width, and angle measurements without having to print out hard-copy.

With Screen Divider, you'll have a convenient measuring tool that runs as an overlay on your computer screen and is fully configurable using only your mouse. Use the intuitive controls to adjust the width of your divider lines to ensure that your on-screen elements are evenly spaced. Add a second divider to calculate Cobb angles. Or use Screen Divider to confirm that two lines are perfectly parallel. Combine this functionality with Screen Divider's ability to measure the distance between any two points on your screen, assist in measuring the angle between any two lines, or determine the angle of any line with the horizontal, and you have the makings of an indispensable part of your development toolkit.