Overview
An inside shutter must fit within the smallest usable width and drop. Check depth, obstructions and squareness first, then measure in several positions without making your own factory deductions.
Measuring for an Inside Mount
Confirm the frame and obstruction clearances first. Then record three widths and three drops using a metal tape. Keep all six readings, choose the smallest width and drop, and leave manufacturing deductions to us. Do not assume a rectangular-looking opening is square.
Measuring Inside Mount for a Square-Set Window
Within the opening, take widths at the top, middle and bottom. Take drops at the left, centre and right. Record the smallest width and the smallest drop without subtracting a fitting allowance.
Measuring Inside Mount for a Window with an Architrave
Measure inside the recess, not across the architrave. Check three widths and three drops and use the smallest of each. The trim remains outside the measuring boundary for a recess fit.