Just finished this downdraft table including a reference stone on the left for flat sanding small pieces. It took less than a half sheet of 1/2" plywood, a 2'x4' piece of 3/4" melanine shelving, and some left over 1/8" underlayment for the bottom/baffle. The 3/4" holes provide good airflow and can also be used as dog holes to keep material from sliding around on the slick surface while sanding. The 4" dust extraction is placed on the top so it won't pick up screw, nails, or small pieces the fall through the 3/4" holes. The table also provides a 40" high work surface for general use as well as sanding… I use it a lot for finish work.