Manuscript Preparation, Copyediting, and Proofreading
Q. For proofreading on paper, how does Chicago recommend indicating that there should be one space between two words rather than two? Even a carefully placed “close up space” mark might suggest that both spaces should be deleted.
A. You can write “equal #” or “eq #” in the margin and a vertical line or slash through the offending space. If there are spacing issues throughout, you should make a general comment at the top of the document that spacing between words should be equalized throughout. Please see figure 2.6 in CMOS for proofreading marks.