It is generally agreed that the stick must be made of organic materials, preferably willow, and not of any artificial materials. All participants must drop their sticks at the same time, usually after a referee shouts "drop", "twitch" or any other agreed keyword. Additionally, no advantage may be gained through either dismantling the bridge or the use of any self-propelling stick devices. The stick must be dropped, not thrown, into the water and any player who is deemed to have thrown their stick is disqualified.