This drill is used to get the players used to physical contact. It needs to be carefully monitored to make sure that it doesn't get out of hand - and is only really suitable for older players.
Set up a normal game with two teams. Normal rules apply except that physical contact fouls are allowed.
Fouls such as pushing, tripping, climbing, wrestling, obstruction, pulling etc are OK. However, watch for studs up challenges, and lunges. These are not allowed.
It is particularly interestng to watch activity at corners and freekicks.
As I said, you need to make sure that this does not get out of hand - but if the players keep within the spirit
of it, they really enjoy this and it does them good.