These are pre-construction brackets for Channel Vision's round (in-ceiling) speakers. They are thin plastic pre-form sheets just sturdy enough to indicate the speaker position and hold the speaker wire until the sheet-rock goes up.
Pre-Construction brackets are nailed or screwed to the studs or rafters before the sheetrock is installed. Their primary purpose is to indicate to the sheet-rock installers where (and what size) to cut holes for the speakers.
They are optional. If not used, you must secure the speaker wire in place between the studs or rafters, measure the exact location, then cut the speaker hole and retrieve the wire after the sheet-rock is installed.