User Guide

Editing Font Metrics
433
Key Glyph
Kerning classes must include a declaration of the key glyph that is used as a
kerning master for other glyphs in the class.
To define a master glyph, add a single quote after its name in the class
definition text:
After you accept the changes made in the class definition string, the key
glyph will get a yellow background in the preview panel.