Retailers sell curtain rods in standard lengths. However, some customers have windows that are wider than the widest available curtain rod. Manufacturers can make curtain rods to order but this is often expensive and the delivery time may be longer than desired. Fortunately, it is possible to increase the width of the rod with inexpensive supplies.
Hold the curtain rod in your hands and extend it to its full width. Extendable curtain rods have one rod inside a rod of a slightly larger dimension. The middle of the rod should be in front of you. Pull both parts of the curtain rod apart.
Place one end of the curtain rod extender into the open end of one half of the curtain rod. Push about 2-inches of the curtain rod extender into the curtain rod. This is to prevent the curtain rod from sagging later. Place the other end of the curtain rod extender into the open end of the second half of the curtain rod.
Slide the curtain onto the curtain rod and hang it up.
Consider making your own curtain rod extender if the final length of the curtain rod is still not long enough. Measure the width of the windows. Add about 10 inches to the measurement because the curtain rod should extend past each side of the window for a balanced appearance.
Subtract the original length of the curtain rod from the width of the window and add four inches to this number. For instance, subtract a curtain rod length of 48 inches from a window width of 56 inches to get 8 inches. Add 4 inches to get 12 inches as the length of the curtain rod extender. The additional four inches is for the 2-inch allowance for each end of the extender when attaching it to the curtain rods.
Purchase a cylindrical metal tube that is small enough, widthways, to fit into the curtain rod. Have the tube cut to your measurement.
Pull the curtain rod apart. Feed 2 inches of each end of the extender into each end of the rod. Hang the curtain.