Quoted from jawjaw:
It's a simple metal flap and mounts to the top back of the cabinet. It uses existing screws so super easy to install. It just stops balls from flying over the supercharger and over the back of the play field. This happens when a slow ball enters the supercharger and then is hit by a fast ball already in the supercharger.
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Yeah I need one of these it just happened to me I got three balls in the super charger and one shot off into the back of the cabinet. I am sure I could make one of these, anyone know the demisions of that metal piece?