When you get an erection at the wrong time and place, needing a quick escape. You tuck you penis into the top of your waistband at a 90 degree angle.
Person 1: Dude i had to go up to the board and write and then i got this massive boner
Person 2: Dude how'd you fix that shit?
Person 1: I 90 Degree Tucked that shit. Thank god for that quick getaway