This is probably a niche item.
I designed them to fit the gaps left at the end of an aluminium panel which I will use for mounting switches in a Land Rover Defender.
More details on my blog:
http://blog.discoverthat.co.uk/2017/02/switch-panel.html
Technical
It is most likely that you would need to download the blend file or import the STL file in to a 3D design app in order to adjust this design to fit whatever it is you are making.