N Cook wrote:

Woodruff keys lock gears/pulleys etc to large shafts, similar to roll pins
(same USA term ?) locate small pulleys etc to small shafts

Maybe this is obvious, but just FYI - a roll pin and a Woodruff key may
be similar in function (locking a shaft to something on the shaft), but
not at all in appearance or application. At least not in my corner of
the world.

Bill