[jthrowsitaway]

Some of the smaller airports that I've been through give you a laminated PreCheck card after they've checked your ID and ticket. You hold onto that for a few seconds until you're called up for the next stage of the process. The officer takes the card, places a PreCheck indicator on the belt alongside your luggage, then un-ropes the metal detector and waves you through. Large airports have dedicated lines for PreCheck and don't require all this.