(mine was recently fixed and the lid is currently undergoing cosmetic surgery involving the sacrifice of a pig and a birch tree), so the mech is understood.
The lever on the lid is clipped in place, and then pushes a plastic rod to the side. There's a cog at one point, which pulls the other side's locking mechanism in. It's all very simple. The cog's axle may break; I've replaced mine with an A2 stainless M4x10 screw....
- Bret