A high port, in addition to giving the tongue relief, also places pressure on the palate of the horse’s mouth when the reins are pulled. Some snaffle bits have a port, but they are most commonly seen on curb bits. Some ports will also have a roller that connects the two branches of the U.
Used improperly, a high ported bit can be very painful or damaging for a horse. Ports that are solid, rather than made of a U shaped bar are called spoons or spades.