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 gaff rigged 4-corner sail. Knowing the names of the sides and corners help understand the running rigging and sail trim of the modern junk sail. The 4 corners of the junk sail are: The 4 sides of the junk sail are: The running rigging for the modern junk rig can be divided into two groups—the "pull ups" and the "pull downs." This is important because the action of hauling one line in a group will be resisted by the opposite group. For example, when raising the sail via the halyard, the pull-downs must be uncleated and free to run. The