What is the chair bar in construction..? Why do we use chair bar..? Benefits of chair bar..? In construction, a chair bar (or rebar chair/spacer) is a small, bent steel or plastic support used in slab and footing reinforcement to hold the top layer of rebar at the correct height and spacing above the bottom layer, ensuring proper concrete cover, uniform thickness, and preventing sagging during concrete pouring, which is critical for the structural integrity and durability of the concrete element