VIC-1020 expansion chassis
The VIC-1020 (known as the VC-1020 in Germany) expansion chassis is a large metal enclosure which provides the VIC-20 computer with six additional expansion slots for cartridges (five pointing upward and one lying horizontally and pointing toward an opening on the the back of the VIC-1020). The entire VIC-20 computer is placed into the VIC-1020 and a male edge connector on the 1020's slot expansion board is mated with the VIC-20's internal cartridge port. A monitor can be placed on top of the VIC-1020, giving the entire setup a PET computer-like appearance. Indeed, the black "CBM" label across the front of the VIC-1020's casing is similar to that used on the the PET line of computers. The choice of sheet metal for this enclosure seems natural, as Commodore had a sheet metal fabrication plant for the production of office filing cabinets and desks.
The VIC-1020's chassis has additional storage space which can be used for the computer's power supply (a pass-through for the power supply is provided). There is also a metal clip on the underside of the lid which can hold the RF modulator.
Slot expanders such as this allowed the simultaneous use of several cartridges on a single VIC-20. This allowed features of utility cartridges (like the Programmer's Aid cartridge) and RAM expanders to be combined. Unlike some other slot expanders, however, the VIC-1020 lacked switches to enable or disable individual cartridges - meaning cartridges had to be physically removed to disable them. This emphasizes what seems an apparent design flaw of the VIC-1020; the monitor needs to be lifted off the chassis and set aside to enable the user to open the lid and access the extra cartridge ports - a cumbersome process if repeated often.