Same word as support:

abutment, agency, back, backing, base, bed, bedding, block, brace, buttress, collar, column, cornerstone, device, flotation, foothold, footing, foundation, fulcrum, groundwork, guide, hold, lining, means, medium, pillar, platform, pole, post, prop, rampart, reinforcement, rest, rib, rod, shore, stake, stanchion, stave, stay, stiffener, stilt, substratum, substructure, sustentation, timber, underpinning