7's Rugby Rules...
Rugby sevens is a variant of rugby football in which only seven players per side feature. Both rugby league and rugby union have sevens versions.
Rugby union sevens
Rugby union sevens is sanctioned by the International Rugby Board (IRB), and is played under substantially the same rules and on a field of the same dimensions as the 15-player game.
While a normal rugby union match lasts upwards of 80 minutes, a normal rugby sevens match lasts in the vicinity of 14 minutes (allowing for injury time and so forth). Competition finals last somewhat more than 20 minutes; each half in a competition final is 10 minutes instead of the normal 7 minutes. This allows rugby tournaments to be completed in a day or a weekend. However, sevens scores are generally comparable to union scores; scoring occurs with much greater regularity in sevens, owing to the fact that the defenders are more spaced out than in rugby union.
The only major rule change from rugby union regarding events on the field is that conversions must be drop goals.