The solenoid and brass plunger work together in an electric interlock door system to control the movement of the door. When the door is locked, the solenoid is deactivated, and the brass plunger remains in a stationary position. When the door is unlocked, the solenoid is activated, causing the brass plunger to move and unlock the door. The door can then be opened. Once the door is open, the solenoid is deactivated, and the brass plunger returns to its original position, locking the door once again.