also known as 'system hack"
It is emptying out the contents of one's bookbag, flipping the bag inside out, and putting the stuff back in the bag. After that, put the skinned bag next to the owner without him seeing you
*Note: not all bookbags can be used, but most can
Jim: "Yo man what the fuck did you do to my bag?!"
Bob: "YOU JUST GOT SKINNED!"
Chris: "He's so stupid, he didnt realize i was skinning his bag"