RulingScreen makes you rule your screen. A simple, easy-to-use ruler that lets you develop and design your app easier.
You can register a shortcut to show/hide your ruler, pretty easily.
You can also enjoy various features, such as moving ruler to suit your needs, changing the color of the ruler, or show the ruler always on top of the screen.
I originally decided to develop it after I found that it is too painful to measure a window size of various apps on the screen. I wished I got a good ruler to make my OS X app development life more fruitful.
If you feel sympathy for it, you might get to like the app.
Thank you for the support, guys!