My Japanese classmates taught me that once you are done eating a meal and using your set up disposable chopsticks, it is a custom to take the strip of paper that protected your chopsticks prior to you using them, place them back into the paper slip, and fold the corner of paper into a triangle.
How we place our utensils when we're done to let servers know we are done. How did this become a custom? How is this done differently throughout cultures? I recall being taught to place both the fork and knife horizontally so that the ends point towards 3 o'clock.