Mitered curtain rods work great for bay windows and other corners where you want the curtains to hang continuously and not end at the corner. A miter joint allows for curtain rods to come together at an angle instead of being straight. It is easy to measure for a mitered curtain rod. If you have one corner, first measure the lengths of both of the rods.
Next, you will need to figure out the angle of your corner. The easiest way is to use an angle finder. You can buy one very inexpensively at a home improvement store. You can also use a protractor or even print a protractor off the internet. If you do print one off the internet, tape or glue the paper on something stiffer, like cardboard. Hold the angle finder up to the wall and read the finder. For a mitered curtain rod with one corner, you will to provide three numbers: the angle and the lengths of the two rods. Confirm with your fabricator that he or she will make the appropriate subtractions for the bracket projection. This ensures that your rod will fit the corner correctly.
If you have two corners, you will need to provide the lengths of the three rods and the two angles. If you have a symmetrical bay window, for example, the angles should be close to the same. The more corners you have, the more lengths and angles you will have to find.
Different fabricators will provide different methods of connecting the rods. So check with your fabricator. Sometimes special brackets will be needed. Lastly, choose your finials, wands, holdbacks and rings, if needed.