Drill sets of holes near the top for the upper set of braces. Drill another set about 2/3 of the way up from the bottom. I used #8 screws. I originally used regular screws and nuts, but have been replacing them with stainless. Save yourself some trouble and use stainless from the start.
Put the structure together, but do not tighten the screws. Prepare the soil where you will plant the squash. Place the trellis where you want it, and pound the vertical poles until they are about 1 ½ to 2’ into the ground. You have to pound one pole a few inches then move to the next until it is fully into the ground. When finished, tighten the screws.
The next step is to add vertical strings for supporting the squash. I use jute twine. At the end of the season I can just cut it off, vine and all and throw it into the compost pile. Tie a string at the top and tie the other end to the lower bar. Leave a little slack. You don’t want the strings too tight. Put 3 or 4 for each face of the trellis.
You need a second set of strings from the lower bars to the ground. I string some wire between the posts about 2” above the ground. I then tie string from the lower braces to the wire to complete the structure.
With 3’ between the vertical poles I plant two squash plants on each side. Normally I plant 4 seeds and leave the two strongest plants on each side. As the vines grow, they can be gently twisted around a string. If your squash variety branches a lot you might need to add extra vertical strings to support them.
I have used these supports for acorn and butternut squash successfully, but now I only grow Mooregold squash. This variety was developed at the University of Wisconsin so it grows well here. Mooregold is flavorful, never stringy and stores very well. I typically get 2-3 squash from each vine.
Growing squash vertically on a trellis saves a lot of space. Another advantage is that the squash vine borer seems confused by vertically growing vines and is somewhat less of a problem.