This is a credit card sized key holder for the two types of keys used to unlock the doors to Resistor.
To use, simply press fit each key into its corresponding key profile; it should be friction fit and hold on without issue. To remove a key, either use the finger scoops at the end of each key blade to lift the keys up and out, or if you printed it in a flexible material like TPU then flex it out.
Rigid Filament (PLA, PETG, ABS, etc) | Flexible Filament (TPU)
There's two versions of the model to accomodate for different material properties. The only difference between them is the tolerance of the Medeco key hole post; the rigid version has a tolerance of 0.05mm (post is slightly smaller than its nominal size), whereas the flexible version has a tolerance of -0.09mm (post is slightly larger). Both iterations should result in a fairly firm press fit where the key shouldn't fall out.
As for other settings, the only important thing to note is how many base layers are present. You want at least two solid base layers, which you should get if you use 0.2mm thick layers or thinner. If you're looking to use thicker base layers, such as 0.3mm layers, open the Fusion file, adjust card_base_layer to a multiple of your layer height, and re-export the mesh.
This model was designed in Fusion, which can be accessed using the Fusion archive file. Many aspects of the model, such as the card thickness, are defined as parameters and can be freely adjusted for quick edits. I'd like to think that each parameter is named obviously enough to be of use.
The bow of the Kwikset key is a bit of an anomaly in that regard, given that the holes for it were modeled by projecting a known good blank's profile into a sketch and tweaked manually. In practical terms, this means that the kwikset_hole_tolerance parameter can't easily be set above 0.2mm currently because otherwise Fusion freaks out. I'm hoping to address this in the near future.