Hello - total newbie here..sorry if this posting is in the wrong section! My fiancee and I recently bought a bi-level home with a lower-level that was only framed out. We recently had some additional HVAC ran in the lower level and drywall put up, as well. When we returned to check the work out, we found these above the doors where the pass-through vents are supposed to go (see pictures)...does anyone know what these are? HVAC guys installed them but apparently we went with an extremely busy company, because we cannot get a hold of them or get an answer as to what these are! Are these just placeholders of some kind? Thanks in advance for any input!