If there's one rule to end them all on the training it pitch it's surely: "Keep them shut."
Almost every team on the planet, from Sunday league to Champions League, indulges in a bit of keep ball (or "the rondo" if you want to get exotic) on the training pitch to start a session.
For those who aren't familiar, players form a circle and zip the ball around within it, with usually two players at a time looking to steal it.
The rules are simple - one or two touch only and if you give it away, that's you in the middle.
Oh, and one other thing. Don't get nutmegged.
Kieran Tierney joined in full training with Arsenal for the first time since his summer move from Celtic on Thursday.
And the Scotland left-back wasted no time making his presence felt following an extended injury spell.
As the Gunners stars ping the ball around the circle, Tierney casually strokes the ball through defender Shkodran Mustafi's legs in the most casual fashion.
It leaves the rest of the squad in stitches and the German looking decidedly sheepish.
Tierney, to be fair to him, doesn't appear to want to rub it in too much.
Making enemies on your first day perhaps isn't the best idea, after all.
The Scot is poised to make his Premier League debut before the end of September - and it could come against Manchester United at Old Trafford.
