Lay the shade sail out flat on the floor of the patio, in the position it will be as the canopy. Hook three turnbuckles to the eye holes on each corner of the shade sail and extend them out full. Shade sails mostly have three points of attachment, which can either be anchored to three posts, or to a wall and posts. For this example, they will be attached to three posts.
Dig three holes, 3 feet deep at the end of where each turnbuckle rests. Make the holes around 6 to 7 inches wide, so that the posts can be installed at a slight angle away from the patio, which will compensate for the pull of the shade sail canopy.
Drill a hole 5 inches from one end of three posts made from 4-by-4 inch lumber, measuring 10.5 feet long. Size the holes to fit eyebolts that are long enough to extend all the way through the post. Secure the eyebolts to each post, securing with nuts on the end.
Place a post into one of the post holes, eyebolt end up. Fill the hole three quarters full with water and pour in quick-dry concrete according to the manufacturer's instructions. Stir the mixture with a stick or stake, and tilt the post slightly out from the patio, ensuring the eyebolt is facing the turnbuckle of the shade sail.
Place a heavy garden chair or other heavy object at the base of the post to hold it in position. Repeat with the remaining three posts. The concrete will set within 15 to 20 minutes and will be cured within four to five hours. Fill the remainder of the hole with soil after the concrete is cured.
Position the ladder next to a post and climb it with a D-shackle. Clip the D-shackle on to the eyebolt, then onto the turnbuckle of that corner of the sail. Repeat on all the posts, which will lift the shade sail into the air. Tighten the turnbuckles on the corners of the sail, which will pull the shade sail tight. Tighten then until the shade sail is taut.