Ordinarily when you think flush left, you think of the line itself as flush left, disregarding the “nuclear level,” where the shapes of the characters themselves may or may not be flush left.
As characters necessarily reside on a body, whether real or not, some characters’ visual left may not coincide with other characters’ visual left.
Pictured above are a few lines of 14-point American Uncial, set flush left. Note the yellow spaces. Those are one-point brass spaces. Obscured are one-half point copper spaces following the em-quad.*
The reason for setting metal type like this is the ease with which it is possible to move characters closer to the edge by removing a brass or copper space, or combination thereof, to achieve optical alignment along the left edge of the page. The space removed can simply be added to the end of the line, thereby not affecting the tightness of the line.
This subtlety can now be achieved with digital type. Nigel French outlines this (see page 114 ) and many other aspects of typesetting in his all-encompassing book, InDesign Type: Professional Typography with Adobe® InDesign® CS2, 2006. (A revised edition is due out July 2010.)
For years the book I have constantly referred to has been Geoffrey Dowding’s Finer Points in the Spacing and Arrangement of Type. I still recommend this book—when it can be found— to the serious student of handset type. But for digital type InDesign Type pretty well supplants it.
*The purpose of the em-quad is to facilitate cracking open the form with less risk of pi-ing the type.
