Patio Design Ideas : Shade sails work by a tension technique - the sails, often triangular, are anchored to tension points which may be close to the bulwark of the residence or to the tops of poles sunk into the ground. They have the plus of being portable: if you trade your home, you can move the sail to your new home and reinstall it for the value of new tension points. Shade structures were once all made from image.