Inside Mount

An inside mount installs the headrail inside the window opening so the blind sits flush within the frame — the tailored, built-in look that shows off trim. It has two hard requirements: enough flat mounting depth for the headrail, and an exact width, because the factory deducts a small amount (typically 1/4"–1/2") so the blind clears the frame without binding. That deduction gap is also why an inside-mounted blackout shade still leaks light at the edges. Measure the width in three places (top, middle, bottom) and report the narrowest — and confirm the deduction against your seller’s measuring guide, since every seller’s rule is its own.