Measure in ¼-inch on the outside window frame using a tape measure, and make a small mark with a pencil. Repeat this on all four corners of the window frame, ensuring your marks are evenly placed at all four corners.
Level the marks. Using a carpenter’s level, place the level on each mark. Draw a thin level line across the window frame. Repeat this on all four corners of your window framing.
Hold a rod mounting bracket up to the level line in the top left corner. Place the top of the bracket against the level line, and ensure it is ¼-inch inward. Mark the screw holes with a pencil. Repeat this on the upper right corner.
Place the bottom of a rod mounting bracket on the level line in the left bottom corner, ensuring it is ¼-inch inward. Mark the screw holes, and then repeat on the right lower corner.
Mount the rod mounting brackets on each of the four corners using a cordless screwdriver and coordinating screw bit. Place the brackets over the predetermined screw markings, and mount with appropriate screws. Place a level on the brackets to make sure they are level.
Place the sash curtain over the sash curtain rod, and snap the sash rod onto the mounting brackets. Evenly distribute the curtains to cover the rods completely on the top and bottom. Bunch the center of the curtain, and then apply the sash tie.