Feed segments within an adjustable feed matrix may be vertically adjusted, horizontally adjusted, and adjusted for rebar thickness. The adjustable feed matrix may be used in rebar structure building. A feed column may include a plurality of feed segments. Each feed segment may include a feed input and a feed output connected by a feed cavity. The feed cavity can include a feed mechanism and/or stabilizing mechanism that allows different thicknesses of rebar to consistently pass through the feed segment to the feed output. A vertical adjustment may adjust vertical spacing of the segments and increase or decrease vertical spacing of the feed outputs, enabling different vertical spacing between rebar passing through segments of the feed column. The feed column may attach to a rail through a coupling. The coupling may be released through a horizontal adjustment, enabling the feed column to slide along the rail and adjust horizontal spacing of the feed outputs.