Dangit, he beat me to it. I was just reading this, thinking "what abou ta spring"?
Now there's 2 ways to do it - compressed when down so that they pop "up" when released, kinda like the shaft of a ballpoint pen -
or on a rotating arm that flips/swings around/along an axis from the side. If you went thso latter route, it would be easy to stop teh wing at 180 deg up w/ just an L or similar bracket it hits against. Actually if you decided manual was okay, thsi way would be very easy too - it rotates on a stud, you loosen a wingnut on teh end of said stuf, you flip it up, then tighten that 1 wingnut. 10 seconds.