A vertical bar on the right side of a window or a horizontal bar at the bottom of a window that is used to move the window contents up and down or left and right. The bar contains a box with square or rounded corners, which together look like an elevator in a shaft. The box is called a "thumb" or "elevator," and when dragged with the mouse, the window contents move correspondingly. When the bar is clicked above or below the thumb, the contents are moved one page at a time. The arrows are clicked to move one line at a time.