This is a set of Corner Radius templates from 3" - 8". This set is designed to be used with 3/4" wood. Works great if you have a router but can be done manually with a Jig Saw / Scroll saw but with a bit more finish work. May add a 1/2" version if requested. Please comment with any suggestions
Example of how this can be used.
https://www.youtube.com/watch?v=CGJWzSdElB4&ab_channel=CarAudioFabrication
https://www.youtube.com/watch?v=fQXoIM5xRbU&ab_channel=CarAudioFabrication
Thanks to @mcds_39299 for catching the error on the 4" version!
The author marked this model as their own original creation.