The Tension Rods come in 5 different sizes depending on your window width. They are simply a telescopic sprung loaded tension rod. So you simply turn the inter rod anti-clockwise, until the rod is Approx. 1 inch wider than the window. Then you simply push the rod together so that it squeezes inside the recess. The rod will then stay in position. If you have a wide window over 229cm (90in) you may wish to order some centre supports to help support the centre of the rod. These are self ahesive but also come with a self tapping screw so you can premanently fix them if you prefer.