When you grow nearly any type of squash or gourd, eventually you'll start to find that you have a lot less space in your yard. Winter squashes -- including spaghetti squash -- are the vining type that like to spread out all over any place you allow them to grow. Instead of allowing them to remain horizontal, try building a trellis and allowing those rapid-growing plants to go vertical. Since squash fruits tend to get really heavy, the trellis will need to be fairly solid in order to stay standing.
Choose a sunny location with at least 2 to 3 square feet per plant. Scoop some compost into the soil and work it in by turning over the soil a few times with your shovel. Your two trellis posts should sit approximately in the middle of the location you've chosen.
Dig two holes into the ground about 5 feet apart and 3 feet deep with a post hole digger or shovel.
Place a 4-inch-by-4-inch wood post, 8 feet long, into each hole and then drop 6 inches of gravel around each post, allowing about 5 feet of post to stand above ground level.
Pour a bag of quick-setting concrete into the remainder of the hole. Pour water into the hole, allowing it to pool slightly on the top of the concrete.
Hold a plumb or level against the post to ensure it's level, and then nail 2-inch-by-4-inch boards against the post on two sides as braces, allowing the boards to rest against the ground and hold the post in place. Repeat the process for the second hole and wait about one hour. The concrete should set in about 20 minutes, but give it a little extra time just to be sure.
Lean a 6-foot-by-6-foot piece of 6-gauge wire mesh against one side of the posts and pull it out from the bottom of the posts far enough to make the top of the wire mesh level with the top of the posts. This will create a tent-like lean-to on one side of the posts.
Secure the top corners of the wire mesh to the posts with fencing staples. Secure the bottom of the wire mesh to the ground by pressing U-shaped stakes over the bottom rung of the wire mesh and into the ground.
Lean a second 6-foot by 6-foot piece of wire mesh on the opposite side of the posts and repeat the steps to secure the wire mesh to the post, creating a full "tent" or A-frame trellis structure.
Plant your spaghetti squash a few inches from the bottom of the wire mesh on the outside of the trellis structure, planting two plants on each side.
Train the squash vines to move up the vertical space of the trellis as they grow. If a vine seems to be growing in the opposite direction, move it gently toward the wire mesh, not pulling or bending the vines. Eventually, your vines may grow up and over the opposite side of the trellis.