For this project I built a trellis for my blackberries. This is how it turned out, I am pretty pleased with it.
The steps to build it were pretty simple. I used thicker boards to serve as the vertical poles and thinner boards to be the horizontal boards which serve as the frame for the blackberries. To give the trellis more weight I add two thick boards at the base to give the trellis more weight and make it more stable.
The overall goal was for the blackberries to grow in a rectangle which would increase in height over time. I will add more horizontal poles as the blackberries grew so they would have something to hold on to as the vines rise in height.
More details about the trellis are in the following video: