A punt is
the concave bottom of a 'better' wine wine
bottles .
The earliest origins of the punt are lost in history but
there is much conjecture. Punts likely existed either for
strength of the bottom of the bottle (especially with
sparkling wine) or in order to form a stable (non-rocking)
bottom in the hand-blown bottles. Today a punt is
unnecessary and exists only because many consumers equate
the presence of a punt as an indication of quality. Modern
glass technology allows bottles to be made that do not
require a punt for strength or stability for either
sparkling or still wines.