Out-of-Square Windows

Few window openings are perfectly square, especially in older homes that have settled. That’s why every good measuring guide tells you to measure width at the top, middle, and bottom and height at left, center, and right — then use the smallest width and, usually, the longest height. A frame that’s out of square by more than about a quarter-inch is a real inside-mount problem: a rigid blind cut to the narrowest width leaves a visible wedge of gap at the wider end. The honest fix for a badly out-of-square opening is an outside mount, which overlaps and hides the discrepancy entirely.