tits on a keyboard
<jargon> Small bumps on certain keycaps to help touch-typists find the home keys (ASDF and JKL;) without looking. They are nearly always on the "F" and "J" of a QWERTY and the "5" of a numeric keypad. The Macintosh, perverse as usual, has them on the "D" and "K" keys.
This term is based on the vernacular American expression "as useful as tits on a boar" (or boar-hog, bull, bullfrog, or many other variants), meaning "not useful".
Nearby terms:
TIPL « tip of the ice-cube « tired iron « tits on a keyboard » tj » Tk » tk