The act of positioning your boner straight up you lower stomach to conceal it in public. It sits with the head pertruding from the top of your boxers.
So you’re in class and that hot exchange student who's V-card you've been wanting to steel decides to bend over to pick up her pencil. This nearly gives you a taste of her pussy sitting so visibly beneath her short skirt, but instead you’re left with a boner. Now without Plip'n your immobile, so by positioning it so that it can nestle into your belly button, it has become concealed.