Blank slot cover
Alternatively
referred to as an expansion slot cover, A blank slot cover is a
small-thin metal piece that covers the back end of a computer case to protect
it from foreign objects, keep air flow proper, and electrical interference.
When installing a new expansion card the blank
slot cover must be removed first. In the picture to the right, is an example of
a blank slot cover, next to two expansion cards.
Tip: With screwless cases, you may not have a screw holding in each blank slot cover. Instead, the blank slot covers are held in place with one thumb screw attached to a metal holder that can be removed after the thumb screw is removed.
Also see: Chassis