A filler panel (also known as a blanking panel) is a flat piece of metal that matches the rack unit (1.75″) of a Server Rack. These filler panels typical range from sizes of 1 – 8 rack units. Filler panels are used to close the openings that are not being used in a Server Rack. The filler panels are commonly installed in the front of the Server Rack, but this is more for aesthetic purposes than anything else. Closing the unused opening in a Server Rack prevents exhaust air from mixing with the cooler intake air. This separation of air allows for the efficient cooling of equipment.
Nearly all rack manufacturers make filler panels. Any 19″ filler panel will be compatible with all 19″ racks.