Pontoon bridge in 638. The army of the Umayyad Caliphate built a pontoon bridge over the Bosporus in 717 during the Siege of Constantinople (717–718). The Carolingian army of Charlemagne constructed a portable pontoon bridge of anchored boats bound together and used it to cross the Danube during campaigns against the Avar Khaganate in the 790s. Charlemagne's army built two fortified pontoon bridges across the Elbe in 789 during a campaign against the Slavic Veleti. The German army of Otto the Great employed three pontoon bridges, made from pre-fabricated materials, to rapidly cross the Recknitz river at the Battle on the Raxa
Junk rig Chinese Junk hull. Among the ships used on the coast of China: Each of the traditional sailing rigs can be achieved using the modern junk sail. The junk sail is a low tech approach to sailing and requires only inexpensive components. Spars are typically of wood. Lines for running rigging are typically 3-strand cordage rather than dual core braid. The sailcloth materials are typically light canvas or tarpaulin, used Dacron from discarded sails, or even PVC sheeting. The junk sail is composed of the following components: The junk sail has essentially the same sides and corner names as the traditional