My favorite punctuation mark right now is the two-em dash. There is very little information about this mark on the web, and all of it is incorrect, claiming that the two-em dash is only used to indicate letters that have been left out of a word. I am here to set the record straight.

First, recall how the ellipsis is often misused;— and mis-kerned;— nowadays. A typical misuse is to indicate a pause in voiced or unvoiced conversation:

“I am not sure . . . let me think about it.”

This is unequivocally an complete violation of the proper use of an ellipsis. The ellipsis is correctly used to indicate when part of a quoted text has been left out. Using it for this other purpose leaves us wondering “Is he pausing in speech or is there something he said that the author is not revealing for some reason?” We often can't tell.

Some sort of dash should have been used in the above example instead. One possibility is the two-em dash:

“I am not sure —— let me think about it,” he said reluctantly.

If the person’s pause was not quite so long, the standard em-dash would have been sufficient:

“I am not sure — let me think about it,” he said sincerely.

The two-em dash is for long pauses that exceed the length of a standard em-dash pause. It is also used when you are hiding a person's identity by abbreviating their name, such as,— “During our expedition to Kathmandu, we encountered a Mr. Q——, a former barrister of London, tending mountain goats in a remote valley of the Himalayas.”