This is UIView category that adds properties that make frame geometry-related stuff less tedious.
For example, you can write:
someView.rx += 100;
someView.frame = CGRectMake(someView.frame.origin.x+100, someView.frame.origin.y, someView.frame.size.width, someView.frame.size.height);
This category is based on (Apache licensed) code from http://bynomial.com/blog/?p=24. Properties changed to even more concise (e.g. frameOrigin -> origin, frameX -> rx)