This is a model of the original hard drive mounting bracket inside a PowerBook G3 (Wallstreet & PDQ, c. 1998).
I modeled this to make a variation (to mount and SSD and some other pieces in the existing bay).
The original has a slightly upturned lip on the side that fits under the heat shield; i forsook that lip to make a piece that could be printed flat. It only needs supports for the little screw holder that sticks out on the side
This is a tight fit into the existing bay; you can make something smaller, but you probably can't go bigger.
The author hasn't provided the model origin yet.