I worked on motoe barges in the Thames Estuary, one as master was an ex saliorman fitted with an iron topsail the Beric of Harwhich. I f you had two cloths such as on the main hatch , you pulled out the aft one first then pulled the forward one so that the forward one overlaps the aft, if you have a second ( older cover to take wear and tear then you start from aft then Forward, corner folds always put in the side never on the head ledges. If there is a single cloth to cover the whole of the hatch, it is usually always left in battened on the forward head ledge then pulled aft over the hatch. This principle was common on coasters, where you could have 3 to 5 layers of canvas, the best on first the worst on last. Then after the clothes are on and batterned down tight you always put across hatch lashings, these are for emergencies such as in bad weather the battern wedges get washed out and protect the cloths from tearing off completly in severe weather. An yes I have been on deck in bad weather knocking in battern wedges along the combings and headledges. Because a barge in a river loading going round to the Medway had 3 inches freeboard and going on the coast it was 9 inchs freeboard for both barges and coasters. I f you think it does not get rough in the Thames to Medway route , I have been of Southend Pier in a Eastly gale and floated the man overboard floats on my lifebouys to such an extant that they where flashing.