Have been asked for advice on making a folding wooden walking stick for a
large heavy man. So its got to be something a bit stronger than usual. Was
thinking of something like using 2 inches (5cm) by 3/4 inche (2cm) in cross
section size.

I searched and read the preferred wood for making aircraft is Douglas Fir,
so i thought that would be good for this stick. (good strength to weight
ratio) but I guess that is difficult to buy already cut to size here in
London. U.K.? Would some kind of building grade plywood be stronger, I
wonder?

The tricky part would be some *self-locking* hinge. Does such a hinge now
exist? I remember very many years ago seeing such a thing (I think on
something agricultural). Would be grateful if anyone had advice on this.
Thanks.