Item Description / Notes

What it is A rectangular sheet‑metal duct section, likely used in HVAC (heating, ventilation, air conditioning), for conveying air.

Size / Dimensions 20″ by 11¼″ (i.e. “11/4″ read as 11.25″) cross-sectional, and 36″ long. So width = 20 in, height = 11.25 in, length = 36 in (3 ft).

Shape Rectangular (flat top & bottom, vertical sides).

Likely Material Usually galvanized steel, possibly other sheet metals like aluminum or stainless, depending on environment. Matte finish or coated.

Purpose / Use Air distribution — could be supply, return, exhaust, or transfer air duct. Installed in buildings, possibly part of a branch run or plenum.

Installation Setting Indoor ductwork; possibly in mechanical rooms, above ceilings, inside walls or shafts depending on system.

Sealing and Connections Likely joined at ends by rectangular flanges, slip‑in connections, seams sealed (with gaskets, tape, or mastic), with fasteners (screws, rivets).