ramsrc,
I believe its does exactly what it says on the tin!
On the aircraft I fly they are soft circular pads on a long threaded bolt that goes inbetween the edge of the aileron (or other flying control) and the rest of the wing/tail fin.
The idea is that whilst the aircraft is parked the flying control cannot be moved by a gust of wind and damage said surface.
I have also seen some real Heath Robinson contraptions that fit in the cockpit that fit around the yolk and rudder pedals, very difficult to get on and off.
Hope this helps.
TBL