set-face-bold

set-face-bold is a compiled Lisp function in `faces.el'.

(set-face-bold FACE BOLD-P &optional FRAME)

Specify whether face FACE is bold.
BOLD-P non-nil means FACE should explicitly display bold.
BOLD-P nil means FACE should explicitly display non-bold.
FRAME nil or not specified means change face on all frames.
Use `set-face-attribute' or `modify-face' for finer control.