Don't damage your aircraft by using a propeller lock. It happens more often than you think. Someone accidentally turns the key with a propeller lock installed. Usually it something innocent like taxiing the plane to the maintenance hangar or to the wash down area. The owner or lineman jumps in the plane without doing a pre-flight, after all you're not planning on flying, you just want to move the plane...but all it takes is a turn of the key to damage a propeller, cowling or bent the crankshaft on the engine.