Tension

Spring rods, also referred to as tension rods, are very easy to install. Using a tension rod will allow you to have your window treatments in place in just a few minutes. Tensions rods do not require the use of any additional hardware such as screws, nails or mounting hardware. The rods are held in place by the use of a spring on the inside of the rod that pushes each end of the rod outward, using much the same principle that a shower curtain rod is based on. You mount a spring rod on the inside of the window sill or molding trim. You will need at least ½ inch of flat space inside the windowsill or molding for the spring rod to rest and hold itself in place. Because these rods are mounted in front of the window glass, the curtain length will be the exact same length as the window itself.
 
Spring rods are usually white or off white. They have rubber ends, which will prevent them from marking or scratching the window molding. It is important to remember that the curtains will cover only the window when hung from spring rods. They will not cover the molding or windowsill because they are mounted inside of the frame.