【CUT AT HOME】 Keego Light blocking strips come in a range of lengths and can be trimmed to fit your windows size. Just cut them with sturdy kitchen scissors or a hacksaw. Standard size: 58.5" x 1.2" x 0.9". Made of light absorbing PVC plastic material. 【HOW THE LIGHT BLOCKER WORKS?】All window treatment must be made slightly smaller than the window opening to prevent rubbing on window frame when blackout shade is raised or lowered, so light may shine through. Light Blockers are an L-shaped piece of plastic that goes in front of or behind your window covering to block the part of the window that is not covered. 【BLOCKS 100% of LIGHT】 Along sides of Blackout Window Blinds (Does not include shade)- Keego Light blocker prevent light gaps on blinds and windows.