Custom plastic extrusion and injection molding to the order and specification of others, including secondary operations in the nature of electromechanical assembly of custom manufactured articles for others; custom manufacture of extruded and injection molded plastic devices, articles and assemblies, particularly in agricultural, industrial and electrical product lines, including gates for surface irrigation pipe and sprinkler package components such as drop pipe, hose weights, u-pipe, drive shaft shields and bells for center pivot irrigation systems