The principle is simple: spin a rod (or rod-like object) fast enough and you can get it to function as a makeshift shield. Of course, this raises questions like how it can be done without injury (human joints have limited articulation), how the rod can get up to speed fast enough to actually block stuff, how the user manages to recover from the exertion so quickly, and if bullets are being blocked, how the rod isn't damaged if it's not stronger than usual. Don't bother. Of course, now we do it for bullets and lasers, but nobody seems to mind a lot because Everything's Better with Spinning.