The river Main not only served defensive purposes, it was also an extremely important transportation route. Geographically, the Main accessed the "Maindreieck". This major Germanic settlement area was located upriver. Downriver, supplies were transported to the Roman military locations. In addition, construction material such as wood and bricks were brought as far as the estuary, to the legionary fortress Mainz/MOGONTIACUM .

The harbour of Fort Stockstadt can be considered the central reloading point for goods at the Main Limes. The quay wall, which could be excavated, enclosed a deep water basin that enabled ships with larger draughts to anchor. Goods were unloaded with cranes.

Further harbours have been discovered by the forts Miltenberg-Altstadt and Wörth am Main. The red sandstone, which was used for building and for stone monuments, was loaded on to barges. Wood from the Odenwald, and also from Spessart, was put on rafts.

At Fort Großkrotzenburg, where the "cohors III Vindelicorum" operated a large tile factory, there must also have been a harbour.