Once, long ago, we had rotor brakes in the 206 that were part of the aircraft hydraulics. You got one chance to stop the blades, and then there was no brake left. I shut down on an offshore platform with a wooden deck, stopped the blades, got out, got the tiedown stick out of the baggage compartment, and saw that the blades had started turning because of the wind. I walked to the left front quadrant and casually jumped up to catch the blade as it lazily swung around. The next thing I knew I was on the deck near the tailboom, almost on the fence, with splinters in my backside and back, and pain throughout my torso. I wasn't sure I could get up, but I finally did, and now the blades were turning at a pretty good rate. I crawled back into the cockpit, started the engine to regain hydraulics, stopped the blades, got out, and the blades started turning again. I finally kept hitting the leading edges with the tiedown stick as they passed overhead, and eventually succeeded in stopping the blades and getting them tied down. I was in no shape to fly back to the beach right then, and didn't want to lose the aircraft because of the windmilling blades, which can turn at a good rpm with a strong lifting wind. After a few hours, my passenger was ready to go and I sort of felt up to flying, and we got back to the beach, but that's the last time I ever tried to stop any blades manually. A rotor brake is an essential investment. If you don't have one, you will eventually learn that.