The linkage designer and tester uses manila folder material and thumbtacks, is easy to build, and gives fast results without needing fancy computer aided design software.

I first made a base by drawing the wing section onto a large piece of manila folder. I then chose points where the linkage would be hinged to the fixed wing section, and then pushed thumbtacks through the back of the base at the hinge points (see the bottommost and leftmost thumbtack in the picture). I then cut small pieces of manila folder in the shape of the proposed links, with holes at the hinge points, and threaded them onto the base thumbtacks. Hinges between moving parts are represented by thumbtacks sliding on top of the base and stuck through the two parts to be hinges.

It’s easy to make a number of links of different lengths and geometries, switching and trying them in search of the best link motion. You can also put multiple holes through a single link, moving the hinge thumbtack from hole to hole.