Most people like a large, bright window that drenches the room with sunlight, but if a security floodlight points at the window, you need to catch daytime sleep or you just prefer dim rooms, the window is a nuisance instead of a godsend. Also, too much sunlight can also overheat a room, resulting in higher summer utility bills. Instead of throwing up the dreaded tinfoil, which many HOAs and lease agreements prohibit, make a set of inexpensive black out curtains.
Hang your blackout curtains on a standard curtain rod with clip-on rings along the top. Install the rod 6 inches above the window casing or higher for better light-blocking. Since your curtains are heavy, screw the rod brackets to a wood wall stud or use a drywall anchor. You may want to use decorative rods instead of standard ones. Dry clean lined curtains. Look at your home from the outside. If there are other covered windows, match your blackout lining color choice to the materials you used on those other windows. Remember, this color may show through the front of your blackout curtains. Additionally, if there are more windows in the room, cover them all with similar lined treatments to unify the windows' appearance.
Measure from the line you drew to 1 foot or more below the windows' casing. Measure all the way to the floor if you want floor-length curtains, which will block light better than shorter curtains. Add 2 inches to this measurement for 1-inch seams on the panels' tops and bottoms.
Mark your seams down and across each of the blackout panel's four edges. Use a straight edge to ensure even, exact markings. The seam lines should be 1-inch from each edge. Pin the two panels together along all four marked edges. Place pins outside of the seam lines you drew.
Tuck the edges of the open 1-foot section of each panel to the inside. Mimic the surrounding seams with your folding, and pin the material in place.