Vessels were built as cataphract, or "protected", ships, with a closed hull and a full deck able to carry marines and catapults. They had a separate "oar box" attached to the main hull which contained the rowers. These features allowed the hull to be strengthened, increased carrying capacity and improved conditions for the rowers. The generally accepted theory regarding the arrangement of oarsmen in quinqueremes is that there would be sets – or files – of three oars, one above the other, with two oarsmen on each of the two uppermost oars and one on the lower, for a total of five oarsmen per file. This would be repeated down the side of a galley for a total of 28 files on each side; 168 oars in total.