Door Sash Tension Rod Zinc Spring Coil used on wood doors, top and bottom to hold your curtain in place when opening and closing the door. Hardware is included to install the two spring sash rods. This product is for the unusual need that pops up where standard sash rod does not fit. Size: 20″ to 36″ this is the stretch limit. Great for campers and recreational vehicles to hold curtains close to window, top and bottom.