A common problem with the “pizzabox” cases on several Mac LC, Performa and Quadra models is that the latches that secure the top can break off. These are brackets that can be glued to the underside of the latches to give them support. It's also a good idea to sand down the hook part of the latches so that they no longer clip to the bottom case, as this will negate the need to flex them to begin with.
This model was designed against a Quadra 605, but will likely work just as well on the following machines:
Mac LC / LC II / LC III / LC 475
Performa 4xx series
Quadra 605
The author hasn't provided the model origin yet.