Reflector elements (usually only one is used) are slightly longer than the driven dipole and placed behind the driven element, "opposite" the direction of intended transmission. Directors, on the other hand, are a little shorter and placed in front of the driven element "in" the intended direction. These parasitic elements are typically off-tuned short-circuited dipole elements, that is, instead of a break at the feedpoint (like the driven element) a solid rod is used. They receive and reradiate the radio waves from the driven element but in a different phase determined by their exact lengths. Their effect is to modify the driven element's radiation pattern. The waves from the multiple elements superpose and interfere to enhance radiation in a single direction, increasing the antenna's gain in that direction.