Banana socket dust cover / protector

I am currently designing an advanced, multi voltage lab power supply. I am working in stages, but had to drill out all the holes for the corresponding banana sockets, for various voltages. As I don't have all the power supplies, or logic voltage levels installed yet, I made this simple cover, to remind me, that the socket is currently inactive.Can also be used to indicate a faulty socket in lab equipment or in university labs, where fuses often blow during student laboratory exercises.