Many users can't get their heads around GDL, and besides, it has its heartbreaking limits. Instead, here's how to generate schematic trellises, fencing, ironwork, cheese steaks and screens using the complex profile tool:
1: Create a new complex profile containing fills describing the pattern. Start with a single fill surrounding one pattern void. Use the Multiply [matrix] function to array the pattern to the required size. Using incremental constraints will preserve the module.
2: Establish the material and SAVE the profile for use in Walls.
4: Draw the new complex profile wall
perpendicular to the surface it will rest against - establish the thickness with the extrusion.
The complex profile has the advantage of quick edits and can produce any cutout.
Dwight Atkinson