The one-handed Q Ruler is a handy little tool that is accessible, and it facilitates efficiency. Those without the use of one arm will find it wonderfully convenient to use, and those with the use of two might discover that it enables them to multitask.
Those hands-on jobs often do require a bit of juggling, so Sangun Lee's invention is certainly a welcome one. A clear description of how it works is unfortunately not provided, but some features can be understood from the image supplied:
With only one set of fingers necessary, the user can draw an invisible line along the length of the object in question. A green numbered dial on the side Q Ruler reads out the precise measurement.