Use an "up, then down" motion. The dominant hand (that's means the "right hand" for six out of seven of you) moves. The base hand ("left-hand") stays put.
Notice: "open-window" uses a single motion.
Start with the window open, then close it. Use a single quick motion. The right hand is doing all the moving.
American Sign Language University ™ ASL resources by Lifeprint.com © Dr. William Vicars