When your with your friends in a local place and while they are sitting down you run up to them take your hand on the back of their head and put it on your ballsack, and yell "Bitch, You've just been potatoe sacked!" or when your girlfriend is laying down and you perform a teabag only say potatoe sack
When you realize you're out of toilet paper and you have to hop down the hallway with your pants down, not wanting to risk getting shit stains on your underpants, to fetch a roll or two.
Make sure you stock the bathroom with plenty of toilet paper. I dont want to have to do a potatoe sack race to the pantry to get a roll.