November 29, 2014
First off, the valance MUST be attached to the head rail for the side returns to work. In other words, if the blinds are going to inside mounted, then the valance will be too.
Anytime a blind is cut or altered, the valance will be slightly wider to hide the mounting brackets. The width is generally about 1/2"-1" wider than the headrail, but this differs from manufacturer to manufacturer.
The other sides, or the returns, are only needed if you decide to outside mount the blinds.
So if the blind is 35 inches wide, then the valance would typically be slightly wider, from 35-1/2 to 36 inches...again depending on who made it.
These brackets, as well as most for slat blinds these days, come with one bracket that can mount on the wall, on the sides or top inside of a window frame.
Basically, choose whether or not you want it to be inside mounted. Even if it was outside mounted, the valance and returns will be measured wider, so it will hide the brackets.
0out of 1found this answer helpful.