PVC pipe is durable, will not rust, is inexpensive and unless it is exposed to the elements, it will not crack or break easily. Consequently it can be used to create inexpensive curtain rods that will last. With a few supplies you can complete this project in an afternoon.
Measure the width of the window you want to cover using a measuring tape. When measuring, be sure and measure from point to point on the frame where you want to place your brackets for the curtain rod.
Measure out a length of 1/4-inch PVC pipe with your measuring tape, using the window measurements that you have taken. Mark the point on the pipe with a marker where your measurements end.
Cut the PVC pipe with a hack saw on the mark that you have made.
Cap each end of the PVC pipe with 1/4-inch PVC pipe caps. If desired, glue the PVC pipe caps to each end of the pipe using PVC glue. Allow the glue to dry.
Screw large hooks into the window frame for your rod, one screw on each side of the window. Slip each end of the PVC pipe into the hooks. The pipe should rest on the open side of the hooks.
If you have a large window to cover, use more than two hooks as brackets on the window frame. PVC pipe will bend if the pipe is very long, therefore, you may need to screw additional hooks in the middle of the window frame to support the curtain rod.