Blackout curtains overlap to block morning sun

The seam is the weak point

Blackout fabric can stop light across the middle of a curtain, but it cannot cover a gap between two panels. At dawn, sunlight may enter through that thin opening as a concentrated stripe, even when most of the window is covered. The overlap closes that route: one panel extends in front of the other, so the edges no longer meet in a straight line that light can pass through.

A small detail with a practical payoff

This matters especially in hotel rooms, where curtain widths and window layouts vary. Pulling the panels together is not always enough if their inner edges merely touch; a slight overlap gives the fabric room to shift without reopening the seam. It will not stop light coming around the sides or above the curtain, but it can eliminate the narrow beam that lands directly on a bed. Before settling in, checking the center seam can be as useful as drawing the curtains fully closed.