Not collapsible, detachable. Imagine hose latches for pneumatic tools, it's something like that. The safety washer thing is a clip that attaches to the pedal adapter to stop it from unlatching.

On my first day with my Promenade Ezy, I had the plastic clips on and ironically one fell off. I simply left them off afterwards. The pedals themselves never ever detached. Maybe my power grips prevented my feet from reaching the pedal release?