In article ,
Martin Borsje wrote:

What comes in must go out!

Wherefore else holes in the fork tube ends (4x)?

Venting to allow hot air out of the tube when brazing, which would
otherwise force itself out through the joint causing spattering of
molten brass or silver. It's not necessary when the tube is open on the
ends, which is the case in the main frame tubes. The vent holes should
be closed by the framebuilder at the end of brazing, as they serve no
purpose after the frame is built. Indeed, they are a water infiltration
point.