Apparently, the portcullis came to be regarded as a symbol representing the gates of the kingdom, that is, the seaports; which were, of course, the seats of operation of the Customs.

What does a portcullis mean in heraldry?

A portcullis (from Old French porte coleice, "sliding gate") is a heavy vertically-closing gate typically found in medieval fortifications, consisting of a latticed grille made of wood, metal, or a combination of the two, which slides down grooves inset within each jamb of the gateway.

What is a portcullis in a medieval castle?

noun. an iron or wooden grating suspended vertically in grooves in the gateway of a castle or fortified town and able to be lowered so as to bar the entrance.