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 box for anyone who likes to build, repair, or tinker with radio equipment and electronic gear. Keeping an ample supply of spare electronic components provides the ham with parts to build a variety of electronic projects, as well as "spares" of components needed for repairs. Resistors, capacitors, transistors, meters, speakers, wire, cable, and even small mechanical parts such as screws, nuts and bolts are typical junk box items. Cannibalizing or removing parts from old equipment is sometimes the only way for an individual to obtain some types of parts, either because they are no longer made, or can only be ordered