Ok Guys, a little later than I wanted to be but I'm crazy busy as usual..
Anyway, here's a render of a quick 3d model I built to best show the set up.
Two aluminium bars with pre drilled holes.
Bolted together at one end, use a nylon washer between the two as this will help free smooth movement.
Also, I've shown where you need to resin and fiberglass over the end to make sur eit locks up against the inside wall of the thigh and then the other, the inside wall of your lower leg, the pivot point (bolt section) should be in a free gap or at least where your knee will bend, so I'd advise, you place this in and before you Fiberglas it in, Hotglue it! Test it with your leg inside the pieces , make sure your happy, then fiberglass it to make it solid.
This should be as clear as it gets.
Oh and a second note* if the inside wall of you thigh or lower leg isn't flat and doesn't allow you do the above like my War Machine didn't then place the bar in a vice and bend it so it has a step , so that it better fits the wall inside the thigh as there may be a step or a ridge to the edge of the thigh piece. Again,you can see pics of what I did there on page 2 of this very thread.