It doesn't take much to be able to do a pat down. The worst ones are carrying illegal weapons much of the time. You have to be able to distinguish between the non-violent hoodlums and the more dangerous ones. This isn't about locking some guy up for a joint, but figuring out who the real bad guys are and building some rapport with those who aren't. The joint smoker you allow to walk away may have information on something more important later on. This isn't something you learn by reading the SOP