The double-headed arrow is a special mouse cursor displayed when a window or window object can be resized. For example, this cursor is shown when you move your mouse pointer to the edge or corner of a window in the Microsoft Windows operating system. The image shows an example of the vertical double-headed arrow. When this cursor is active, you can drag the object up or down to increase or decrease its vertical size.
A horizontal and diagonal version of the double-headed arrow may also be available. Below is an example of the diagonal double-headed arrow, shown in the bottom-right corner of a window in the program Notepad. This arrow is used to resize a window.
This cursor is only visible for a window when it's not maximized and capable of being resized.
Mouse pointer, Operating system terms, Resize, Size handle, Two