The sign for "window" shows the opening and closing of a window.
Use an "up, then down" motion. The dominant hand (that's means the "right hand" for six out of seven people) moves. The base hand ("left-hand") stays put.
WINDOW:
"Open-window" uses a single motion.
OPEN-WINDOW:
To indicate a closed window, start with the window open, then close it. Use a single quick motion. The dominant hand is doing all the moving.
CLOSE-WINDOW:
Notes: