Mine are hinged on the bottom, I never tried hinges on top. The only issue is that you want them to open to slightly beyond level so they drip outside if it's snowing or raining and then you need a pulley up high to pull them closed . I have ropes to close mine, but both are then joined and go down as 1. On that one I have a knot to show how far to open them. I use a boat type cleat to tie it off, and the knot always gets placed at the same spot on the cleat. If I go too far and let them rest on the roof I'm barely heavy enough to lift them, and I'm not a light weight by any means.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.