Related Clues:

• Printing spaces
• Nixon has two
• Halves of 1-Across
• Widths of typical characters
• Lengths of some dashes
• Off. above a midshipman
• Off. at sea
• Typesetting spaces
• Thinning in the middle?
• "Ninny" uses three
• Jr. naval officer
• Halves of ems
• The two in none?
• Naval officer below lieut
• Half of nine