An anchor is a weighted hook that moors a ship. It’s frequently found in period armory, as in the arms of Skipton, c.1410 [TJ 1507].
Heraldry has special terms for some parts of an anchor: the shank (upright) is blazoned the “beam”, the stock (crosspiece) is the “timber”. The timber is to chief by default, but anchors inverted were not uncommon in period heraldry. An “anchor fouled of its cable” has its cable wrapped around the beam.
There were some variation in the heraldic depiction of the anchor; the illustration is taken from de Bara’s Blason des Armoiries, 1581 . For related charges, see grappling iron.
Molle of Norwiche bears: Sable, three anchors argent.
John of the Rudder bears: Gules, an anchor Or.
Aethelstan Osricson bears: Or, three anchors in pall, rings to center vert.