Step 1 Decide between Inside or Outside Mount
First, you’ll need to decide whether you want inside mount or outside mount blinds. Inside mount blinds, as the name suggests, mount inside your window frame, while outside mount blinds mount outside or over the window frame.
Next, check the casing depth. If it is less than 2 inches, an outside mount is required. Also check the squareness. Measure your window casing diagonally in two places. If the two diagonal dimensions are not equal, an outside mount is recommended for optimal function and aesthetics.
Inside mount blinds will give you the cleanest look overall, while outside mount blinds offer more variety, as the window frame size doesn’t matter when choosing them. They’re also a great choice if you’ve got obstructions inside the frame, such as window openers.