Your basic old PC has slots for cards. You knock it out to open it up.
I'm asking a question I should know the answer to, but don't.
On the back of my PC case, near the bottom, are two knock-outs (3" x 1/2"). Components could go there, but what sort of components might those be? There are two holes on either end, which I suppose are used to attach them to the case.
Sorry for my ignorance. Please enlighten me. Thanks.

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