No, the TSA agent when you show your ID and PreCheck eligible boarding pass, at a time when PreCheck is not operating. Typically they then give you a card, which you then hand to the other agents at the belt/scanner. They'll place blocks on the belt before/after your belongings to designate them as belonging to a PreCheck passenger (i.e. you still get to leave everything in your bag) and you get to go through the metal detector instead of the body scanner (without removing your shoes etc.).