If you are going to be using posts you will want to use as solid a material as possible. The larger your sail the more tension that is going to be involved in order intended for it to not sag. Steel posts are the finest option but you can also use wooden posts if involved. The larger the diameter of the material the more support you are going to have. Your holes designed for your footings should be a minimum of 4 feet deep or at least one third of your walk through height should go into the ground. Once you have determined the measurements of your holes you will want to commence digging. It is significant to notify the proper authorities of your up coming dig so that they can create positive that there are no electrical or utility lines buried. Use standard methods such as shovels or augers to dig out your holes.