I'm posting colars. If it was the hot guy thread, i'd be obviously posting shirtless pics. And you guys should get your hot chick thread back IMO as well.
It means to reach up & pull on your shirt collar & release it with a flick, you do this when you're very pleased with something you've just done, The Fonz used to do it, there is another reason however, it could suggest that you're a pimp, strutting your stufff.