The punctuation marks you use (and where you put them) can completely change the meaning of what you write. "Twenty-odd ducks" is an estimate of how many are waddling by, but "twenty odd ducks" would not only be a big group, they'd be a very strange looking. Imagine this without the middle period and the comma: "The king walked and talked. A half hour after, his head was cut off." Oh no - a beheaded king that can still walk and talk!
Along with the Eats, Shoots & Leave: Why, Commas Really Do make a Difference! and The Girl's Like Spaghetti: Why, You Can't Manage Without Apostrophes!, Truss and Timmons's punctuation hilarity now includes hyphens, parentheses, quotation marks, colons and more.