J6 through J8, supposedly all sticking to the same "Northern" theme as well as J5, alluded to the change between summer and winter and the cold setting in during the latter. I start to wonder whether the "day" and "night" in this riddle are metaphors for summer and winter as well. In that case, and if it's a wintery implement, the orientation during use would supposedly be the upright one.
It's not a rowboat, either, though, to address the typical traditional mode of transportation in Saimaa. You may take a small rowboat out of the water both at night (so it doesn't float away) and during winter (so it doesn't get damaged by ice) and turn it over so that rain and snow won't accumulate inside it, but you don't stand it on end.
German has the idiom "they fold up the sidewalks at 6 PM" for a particularly rural/quiet/deserted settled area, that wouldn't happen to be based on an actual Finnish custom, would it?
(AmE prefers to speak of rolling up the sidewalks, I see.)
... the shutters you put on the ground floor windows during a winter that'll have your house snowed in 1+ stories high, to prevent the pressure from the snow breaking the glass?
