Hello. I would really appreciate any ideas on how to fill the holes left in our concrete floors when the old warm air heating was removed. Below the vents is the metal ductwork running back to the old boiler. We have seven of these holes to fill so that new carpet can be laid and I am not too sure how best to go about this. I was thinking that I could maybe screw brackets in the sides and use these to attach wood on the top, but the holes are not large enough to be able to get a drill into. Appreciate any ideas. Thanks.