Norm writes –
[Here are the] basic materials to build channel to hold four 3 gallon pots in drip system. I chose these materials because of either their availability or cost. The fence boards cost 99 cents(US) each at Home Depot. The furring strip was 65 cents,(I substituted a couple pieces of scrap 1×4 for part of the furring strip), the plastic is greenhouse covering, but could be common 6 mil plastic sheeting if protected from the sun. The ground cloth is used to keep the sun from hitting the nutrient,and help hold the pots in place. This prevents algae growth. Any non metal material that will block the sun could be used. There are any number of substutite materials that could be used instead of the ones shown as long as the basic rules of no toxic material or any metal other than stanless steel in contact with the nutrient.
Drip system – Link.