- Measure the exact inside width of window frame from one inside edge to the other. Take three measurements, one near the top, one in the center and one near the
bottom. Record the narrowest measurement.
- Measure the exact height in three places, left, center and right from top edge of opening to top of sill. Record the longest measurement.
- Do not take deductions on inside mount measurements. The factory will take an allowance for operating clearance.