Typically R is the key to lock prop rotation.

I don't no why but it dosen't work

Pretty sure in most prop hunts on garry's mod, you can't lock your prop, because it's actually locked by default. On your screen it will appear as moving when you rotate your camera, but all props have a fixed orientation. You can test by moving around your camera and asking your friend if they can see, but usually that's the case.

I don't no why but it dosen't work

I think this version of prop hunt doesn't have the locking mechanic