Plunger Detent

Slipping beneath the front door after riding the elevator upstairs, I found a retractable ballpoint pen lying flat beside the shoe mat. Its transparent barrel offered a clear view of the stepped cam mechanism inside. Bracing my sneakers against the hardwood floorboards, I pressed both palms against the top plunger and leaned my full body weight downward. The internal spring yielded under steady force until the rotating plastic cam pivoted thirty degrees with a loud, hollow snap, locking the brass tip forward. Pushing the plunger a second time cleared the detent, snapping the shaft back instantly. The mechanical cycle functions with absolute reliability.