The one prevailing law during a gangbang
that creates order from disorder. After a reasonable period of time has passed, the gentleman who's "on deck" may tap the shoulder of the gentleman currently "at bat," and the latter gentleman must step aside and let the next guy have his turn.
This rule also works for drinking at a water fountain.
The Tap Rule was popularized during one particular scene (I believe it was No Holes Barred 4) where a certain anonymous man repeatedly ignored the aforementioned shoulder tap and was sternly reminded by one the men standing by to, "Respect the Tap Rule."
Rather than let the normally enjoyable experience turn to violent anarchy, the man relented and allowed the next gentleman to put his hoohoodilly
in the female participant's cha-cha
, thereby preventing possible bloodshed.