Thank you for educating us Gunner. I think I saw that Mufulira engineering squadron demonstrating how they build one at the Zambia trade fair

It’s a steel structure across a river normally built by military engineers to enable the quick movement of soldiers during military operations. They’re temporary bridges and therefore do not cost as much as long-lasting ones. An acrow bridge is also easy to dismantle once you no longer need it after your soldiers have crossed so that the enemy cannot use it.