Many houses in Europe and north America have basements with windows located below the ground level, deprived from sufficient sunlight. Placing a reflector would enhance the natural light levels inside the underground space. "Modulight" is a modular reflector composed of 10 types of building block, which shall be purchased in appropriate numbers. The blocks are then assembled to fit inside the window outer space. The modules are designed to give flexibility both in size and shape of the final assembly. The overall assembly can vary in width and height, and can have bigger or smaller corner chamfers, as required by geometry.