Block-out curtains are made from heavy fabrics or materials that are thick enough to block out most of the light that would normally enter a room. They may not completely block out all light, but they can significantly reduce the amount of light that enters a room Blackout curtains, on the other hand, are specifically designed to block out all light. They are made from a special type of fabric that is tightly woven and thick and is designed to completely block out all light from entering a room