Many brief-writers use fully justified text, so that the text lines up with both the left and right margins. I don’t. When I make the typography decisions, I use left-justified or left-aligned text, with a “ragged-right” margin. This is not a matter of personal preference. It’s a matter of readability. If the text is generated by a word processor (e.g. Word, WordPerfect) rather than professionally typeset, left-justified text is easier to read because it avoids odd gaps between words. But don’t take my word for it. Consider these authorities:
“Except in the hands of a skillful typographer, fully justified text can be harder to read than unjustified (‘flush-left’) text. This is always true for office documents, and especially when they are unhyphenated as well. Forcing the text to both margins may result in lines with word spacing that is too wide or, worse, unevenly distributed across the page.... Setting the copy flush left has its own advantages, too: the uneven right margin gives visual clues that help the reader find the beginning of the next line. Readers don’t lose their place in the copy as often.” Bryan A. Garner, The Redbook 92–93 (3d ed. 2013).
“In my law practice, I almost never justify text. Why’s that? The justification engine in a word processor is rudimentary compared to a professional page-layout program. I find that word-processor justification can make text look clunky and coarse. Left-aligning the text is more reliable.” Matthew Butterick, Typography for Lawyers 136 (2010).
“For desktop publishing, then, the choice should be different. According to some experts, keeping the text left-aligned affords the greatest legibility because there is no adjustment needed to word spacing and because the resulting ‘ragged-right’ margin adds variety and interest to the page without interfering with legibility.” Ruth Ann Robbins, Painting With Print: Incorporating Concepts of Typographic and Layout Design into the Text of Legal Writing Documents:, 2 J. ALWD 109, 130 (Fall 2004).
“Do not justify your text unless you hyphenate it too. If you fully justify unhyphenated text, rivers result as the word processing or page layout program adds white space between the words so that the margins line up.” U.S. Ct. App. 7th Cir. Requirements and Suggestions for Typography in Briefs and Other Papers.