I asked another writer friend why my computer won't supply me with the right sort of dash when I need it, and seems to make an arbitrary decision about the length of dash. This led to a discussion on which sort of dash should go where. For the benefit of anyone else struggling with this, this is what he sent me. Thank you James!
These are shorter than en-dashes and are only used to link two words or parts of a word:
There is a trend towards fewer hyphens.
• Don’t hyphenate compound nouns, like dressing gown, dining room, etc.
• BUT compound adjectives are hyphenated when they qualify a noun:
half-open eyes or the eyes were half open
• Be consistent: use ear ring, earring or ear-ring, but use the same one all the way through a piece.
• Sometimes they are necessary to make things clear
thirty-odd people ≠ thirty odd people
extra-territorial rights ≠ extra territorial rights
re-cover ≠ recover
re-creation ≠ recreation
re-sign ≠ resign
• No hyphens between an adverb of degree and the following adverb or adjective: slightly ill, not slightly-ill.
This is as wide as the letter n: –
• It indicates a pause: “Paul could hardly stand – his legs were covered in blood.”
• Parenthetical, with space before and after.
(Note on autocorrect: Word converts a hyphen to an en-dash when you follow it with a space, a word and either another space or a piece of punctuation. If you insert a hyphen between two words it’ll just sit there, even if you put spaces around it. Put another space after the next word (then take it out of course) and the hyphen will change to an en-dash.
This is twice as wide as an en-dash, a bit wider than a letter m: —
It is only used to show cut-off dialogue if speech is interrupted.
The dashes go inside the quotes if other punctuation is replaced, outside if not.
There’s no keyboard key for this, just as there isn’t for the en-dash. But in this case, there’s no Autocorrect either. Ctrl+Shift+m makes a good shortcut.
How to set up a keyboard shortcut in Word:
Menu Insert Symbol. If that gives you a choice of Browser and Advanced, pick Advanced.
Find the em-dash in the list of symbols – on my version it’s about half way down and a little right of centre – it’s distinctly longer than the en-dash on the top line – and select it. (If you don’t want to set up a shortcut, just click Insert to drop the symbol into your document at the current insertion point.)
Click on Keyboard Shortcut.
Press the key combination you want to use, check it’s okay, and press Assign.
Press OK, then Close on the previous window.