Measure and note the width of the trellis. Mark the center of the top of the trellis. Once you have decided where to hang your trellis, measure to find the center of the hanging location and mark it. The trellis should be centered to the porch opening, window or other architectural structure.
Drill holes through the trellis no more than 3 feet apart. Cut a 2-inch length of PVC pipe for each drilled hole. The sections of pipe will serve as spacers. Holding the trellis on the wall where it will be installed, pass the tip of the nail through the hole in the trellis and tap it with a hammer to make a small indention. Make a small mark on the wall near each indentation so the indentations will be easier to locate later. Take the trellis down. Drill horizontal pilot holes through each indentation. At this point, install wall anchors in the holes if you are not installing the trellis on wood.
Support the trellis on the wall so the holes in the trellis are aligned with those in the wall. Begin installing the trellis by placing a washer on a hole in the front of the trellis. Pass the point of the screw through the washer to the back of the trellis. Place a spacer on the threaded portion of the screw and put the tip of the screw into the pilot hole or wall anchor. Tighten the screw with a drill and driver bit. Continue screwing the trellis and spacers to the wall until the trellis is securely attached to the wall and all of the spacers have been used.