Inserting the Yellow Pin

Yellow pin in my right hand. Red plate in my left. Step, click, step. The black wall had a round hole—a round pinhole hiding right at waist height between two glossy black 2x4 bricks. Round hole. Round yellow pin. It fits. Has to fit. I squared my shoulders, thrusting the yellow pin into the circular slot. Squeak. Friction tight. I slammed my palm against the outer edge. Clack! A sharp hollow click echoed deep behind the ABS masonry, and the whole column shifted backward half a stud, revealing a blinding slit of lime green light beneath.