Boom (navigational barrier)

A port chain or electric chain was a buoyant massive barrier chain that was stretched along the surface of the water to prevent ships at the drive-through in the middle ages. She had the task of preventing unauthorized or unwanted shipping, such as increases or road ride from the port or driving on a stream.

The chain which barred the Golden Horn during the siege of Constantinople in 1453 Opel became known. Captured harbor chains were often carried away by the victors as war trophies. The city of Genoa kept the chains of 1284 in the Battle of Meloria defeated Pisa. The chain port of Marseille was brought to Valencia after the victory of Aragon in 1423.

The strategic importance during the Crusades became the Chain tower of Damietta. In the Kingdom of Jerusalem, a court was responsible for the maritime and shipping law as well as for the collection of duties as a " chain inch " ( Cour de Chaine; Chaine = port blocking chain).