My simple way to pin is:
1) Remove bolt at stock hinge
2) Set stock aside
3) Observe small pin near button (inaccessible when stock is open)
4) Punch small pin inwards (careful the button could fly out)
5) Remove the button, followed by a spring, then the small pin you drove in
6) Find a .40 S&W or a .45 ACP empty casing (one fits better than the other)
7) Put empty casing in place of spring
8) Reinsert button on top of casing
9) Hold the works together & slide stock back into kit
10) Replace the bolt at stock hinge
It pins the stock in a neat manner so you can't see the method of pinning. And if you decide to undo the pinning you can always replace the original parts while maintaining a original look.