The posts that support a shade sail ought to be at least 8 feet in height. The true height of the sail is four to six inches lower than the height of the post because the hardware is mounted somewhat lower than the top of the post and the sail is angled slightly downward in the centre. As a consequence of this, if the posts are between 8.5 and 9 feet in height, the sail will actually be higher than 8 feet in the middle. In the middle of the sail, the height will be closer to 7.5 feet if the posts are 8 feet tall.