Very simple really
The battery-door of my old trusted Spektrum DX3R-radio had a little lid broken of and did not held tightly anymore.
I found another STL for a DX3 … but that radio did not havge the same dimentions, as I noticed after printing .. so designed a new door myself.
Designed a prototype, tested, made some modifications … and the new door fitted realy nice.
Printed mine in Polymaker black which unfortunatly shows the 3D-lac that I use on the printbed. (Those are the white marks on the part).
The author marked this model as their own original creation.