This is one of a number of parts for the Ghostbusters Containment Unit Mod for the Stern Ghostbusters Pinball "Pro" Version only.
This part is the Containment Base Plate & Locking Pin.
Search "swinkscontainment" for the other parts, you will need:
1 x Containment Base Plate & Locking Pin
1 x Containment Cabinet
1 x Containment Bulb Set
1 x Containment Cabinet Door
It would be best to purchase this in Grey or Black.
Contact Swinks Pinball for the manual of how to assemble into your game.