The actual climbing portion of the trellis is a stiff fence material, 48" tall with 2x4" gaps. It's turned on its side and run vertically up from one side of the garden bed, then looped over (about five feet high) and run back down to the other side of the bed.
By itself, this would be pretty floppy (especially with the weight of some mature squash hanging from it). Therefore, we made a support frame from 3/4" galvanized pipe. Two six-foot pipes form the uprights, buried a foot or so into the ground and then screwed to the garden bed frame with pipe straps. Two 90-degree pipe elbows connect the uprights to a four-foot cross bar (which, of course, should match the width of your own garden bed).
We only use one such frame per trellis, and it stands right in the middle of the trellis. The fencing material runs inside this frame with a rounded arch at the top. We use plastic zip ties to secure the fence to the pipe along the sides and at the center of the cross bar. I'm actually not sure how well the plastic will hold up to extended sunlight, so perhaps wire tires would work better. I guess we'll find out.
|With one end buried in the dirt,|
a pipe strap keeps the frame from leaning
|Zip ties secure the fence to the frame|