Decide how "temporary" your needs are for a sun shade. If you want something you can quickly put up for an hour in the afternoon when you read the paper, then take down when the sun passes the maple tree, it will obviously be smaller and of less sturdy construction than something you want in place for every hot sunny day in August. The directions that follow, therefore, will guide you to making a temporary sun-shade that should probably be taken down on at least one side whenever it is rainy or windy. References offer some options for heavier-gauge rigging, varied fasteners and long-term temporary supports. Both the amount of use and the unique configuration of your patio, house and yard will determine exact needs.
Measure the area you want to shade. Spend parts of a sunny day marking your shade area as the sun moves. An easy way to do that is to put small pieces of masking tape on the floor to outline the maximum area for your shade.
Outline the dimensions of your shaded area on graph or other gridded paper. Choose three points of your area to extend. These points should reach out toward fixed objects to which you can attach your shade. Fixed points might include the top of the patio door, a window frame on an adjoining wall, the garage, a tree, an upstairs window or a tall fence. You need to be able to put a screw-eye into each of your three points and attach a nylon line extending from one corner of your shade-cover. Use your three extended points to draw a triangle just big enough to enclose the area you want to shade. This determines the dimensions of your shade-cover, sometimes called a shade sail. When you measure the extended lines to your fixed points, you will know how much nylon line you will need to secure your sail.
Enclose your triangle in a rectangle. The rectangle represents the amount of fabric you need to buy to cut your shade in a single piece. To save on fabric, you can seam several sections together to make your triangle. Sew each side with a 2-inch turnover seam. Set a grommet in each corner of the triangle.
Set hooks into your fixed points. Ideally, all of them are at a height above that of anyone seeking shade. With few fixed points, however, a deck rail can serve as one point, so long as you are willing to watch for the rope and duck.
Thread a length of nylon line through each grommet and tie it securely to the corner of the shade sail. Tie the other end to one of the fixed-point large-eye hooks, unless you can just tie the rope around a post, rail or tree. Enjoy your shade.