Central ducted vacuum cleaner system flap valve backing plate for mounting switched inlets/flap valves onto wall studs.
The thick part is for when it has to be fixed onto a stud wall.
As it's light, maximise the saving on postage and buy some of the related parts below, and maybe dustbags and the filters or a new floor tool.
At the moment, standard postage within Australia is capped at a maximum of $20!
We at TVD carry out in-home repairs on built-in ducted vacuum systems in the Perth area from $135, call 08 9362 6044