What does Blank slot cover mean?

Blank slot cover meaning in Computer Science Dictionary

Alternatively called an expansion slot cover, A blank slot address is a small-thin material piece that addresses the back end of some type of computer case to protect it from foreign things, hold ventilation appropriate, and electric disturbance. When installing a unique growth card the empty slot address must be eliminated first. The picture is a good example of a blank slot cover, close to two development cards.