The next step was designing the triangle lock. I wanted something that could simply be rotated to unhook or unlatch the flap. I decided to go with a triangle, as it proved to be the sturdiest for something so small, as opposed to a flat rod with more potential for breaking.

The triangular piece would be attached to the small gear underneath and that whole piece would rotate freely, allowing the larger gear to turn the lock into place. I made a small gap in between the triangle and the small gear, so that a thin piece of card stock could fit underneath and hook triangle in place. A matching triangle would be cut out of the card stock with just enough space to allow the triangle to pass through when rotated to fit.