Height variance is the difference in height between your attachment points, whether you're using posts or attaching to the side of an existing structure. We consider height variance to be one of the most important factors when planning out your shade sail and the main reason we suggest quadrilateral sails over triangles. When all attachment points are the same height, the sail is flown flat and as well as not looking the best, creates a number of problems that affect the longevity of your shade sail. One issue with flat shade sails is their tendency to encourage pooling of water, which can lead to your fabric stretching and possibly tearing. With a triangular shade sail, it's impossible to twist the fabric meaning you can only fly your sail on a single plane. If you are flying triangle sails, we recommend varying your post heights to allow for water run-off. With quadrilateral, 5 and 6-point sails, by varying post heights you can twist the fabric giving the appearance of multiple triangular shade sails. Using a quadrilateral shade sail also allows for maximum coverage while still attaining an aesthetic look. A hyperbolic shape is attained by varying post heights on diagonally opposite corners. Not only does this create a spectacular look and reduce water run-off but this shape also performs the best in the wind.