I was challenged to design a chair such that all parts can be made on a laser cutter. This means no threaded fasteners. I'd like to highlight the joinery method I implemented during this project to permanently connect two co-planar sheets along their edge such that all degrees of motion are restricted. 

The C-clip isn't mechanically necessary, but it strengthens the butterfly wedge. Without it, it the mechanism would fail along the base of the butterfly wedge's wing. Four wedges are inserted under the butterfly wedge to create a clamping force.

The wedges have teeth that match with the butterfly wedge to lock them in place once inserted. This makes this joint permanent.