Whenever you try to grapple an object that you are actually partially inside of, you are flung into the air (or any direction really) at great speed.

This lets you skip huge parts of levels, and access areas that you wouldn't otherwise be able to access normally.

Check out my video guide for how some of the setups work. There are heaps of other places that you can use this glitch, feel free to experiment and find your own flings to explore the levels your way!