Now, measure the length from the top inside casing of the windowsill. At least 1 inch of flat surface will be needed on the inside casing in order t car recycling equipment o attach the brackets. For outside frame mounting, youll need to measure the overall width of the area to be covered. Hang your min how to lose weight fast i blinds outside of the frame if there is less than 1″ of flat surface on the inside casing.