[header] How to hang sheet metal in your cabinets [title] Lay a straight edge on the bottom shelf of the cabinet. [step] Measure the inside surface of the cabinet, by first laying a straight-edge face flat on the bottom shelf of the cabinet with one end of the straight-edge sticking out of the cabinet a few inches. [substeps] Slowly close the cabinet door until it is lightly touching the straight-edge. 
Mark a pencil mark on the door where it touches the straight-edge. Move the straight-edge over at least a couple of inches and make a second mark.