The concept of "o'clock" is expressed by touching the dominant hand to the top of the non-dominant wrist. This sign provides an example of what is called "numerical incorporation." The dominant hand forms a "4" handshape and then touches the top of the non-dominant wrist in the location where a person would wear a watch. Some people touch the base of the 4-hand to the wrist. Others touch the tip of the index-finger of the 4-hand to the wrist, either way is fine. I prefer to use the base of my 4-hand since it just feels easier.
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