2: To add a virtual brick on a friend's bebo profile, saying Slag? along with your name, in order to portray your disgust for that person.
3: A slag scout will write the word slag on the brick of a slag's house, so that a slag hunter can then identify the house of the slag, and then go and hunt the slag.
"Uurgh, you slagbricked me, you slag."
Apprentice Slag Hunter: "That house has a slagbrick on it. We better move."
Master Slag Hunter: "Right, you strap this bomb under your shirt, knock on the door and look drunk."