The mount refers to the way you will hang your window treatment, either inside or outside the window opening.
Inside mounts are mounted inside the window opening that is recessed from the wall. An inside mount provides a clean look and is probably the most common way to hang blinds today.
The minimum window sill depth for an inside mount varies depending on the product. The depth required for each product is listed under its specifications.
Outside mounts hang outside the window opening and are mounted either on the wood frame or above and beyond the wood frame. Outside mounts are great for doors, for windows with obstructions (such as security-system hardware), or for windows with a very shallow windowsill depth that would make an inside mount impossible. An outside mount can also be used to make a window appear larger, or to hide an unattractive window.
A blind or shade referred to as side mount fits within your window frame and is mounted on the left and right sides. A side mount option may be required for special situations. Select products come with a side mount option if an inside or outside mount is not an option. Products for which this is available will let you choose between inside, outside or side mount when building your blinds or shades.