Big airplanes like the China Clipper that came before the days of hydraulic assist had control surfaces too large for the pilot to be able to move them when in flight. To solve this, the ailerons were actually free floating, with a small tab at the trailing edge that was controlled. When deflected, this tab pushed the aileron in the opposite direction aerodynamically, thereby causing the airplane to roll. So it works like this:

1) stick goes left
2) left boost tab goes down (YES, down)
3) this pushes left aileron UP aerodynamically (NOW I get it!)
4) same thing in reverse on other side
5) plane rolls left

It's all about using leverage - that's why these planes had very large control surfaces chordwise - to get the torque that could be exerted by the boost tab up. All in all, it's a really elegant solution.

See if you can find a good picture of a china clipper parked - you might be able to see that both ailerons are drooping.

See, Dr. King - I was listening that day in Flight 2!