A pair of barnacles is a pincer to be clamped on an unruly horse’s nose; it was sometimes used as an instrument of torture. It may also be termed “a pair of breys”, especially for canting purposes, as in the arms of Geneville or Joinville, lords de Broyes, 1255 [ANA2 222]. Barnacles’ default orientation is with the hinges to chief; they were also frequently found “extended”, or spread fesswise, in period armory, that fact being blazoned.
Barnacles were originally drawn more realistically, but had assumed a stylized form by the end of period. The first illustration is taken from Gelre, c.1370 ; the second, from Legh, 1576 . The latter is the form most usually found in modern heraldry texts, and thus in Society emblazons.
Nicolin Bray bears: Gules, a pair of barnacles argent.
Penelope Stoddard bears: Sable, in pale three pairs of barnacles extended Or.
Brigit Ní Sheachnasaigh bears: Per bend sable and argent, a pair of barnacles counterchanged.