The art of claiming items in a community fridge by planting a toothpick flag. You may plant it directly into any food item, or tape it to the side of a beverage. Becomes necessary when writing your name in sharpie doesn't cut it.
Once a system of flag planting is in place, you may also use it to claim un-flagged items. They'll learn the necessity of flag planting very quickly.
"Dude, John keeps stealing all my taquitos."
"Did you write your name on them?"
"That's the messed up part man, I did!"
"You better start flag planting."
"I've been forced to start flag planting to keep these savages off my party leftovers."
"Dude, who flag planted my PBJ?"
"That's your own fault, Tim. You know how it works around here."
A home-made tiny flag constructed with a toothpick and one of those tiny page-marker post-its. Usually used for flag planting. Alternatively, one of the manufactured country flags commonly used in food arrangements can be used if you and your roommates are of distinctly different ethnicities.
Ever since Jim moved in, our room has become completely filled with toothpick flags.