This mount was designed to modify and adapt a FDn lens to use it with EF DSLR Cameras, along with one of these parts:
Aperture Arm 3mm
https://shpws.me/MZvG
Aperture Arm 10mm
https://shpws.me/MZvI
For more aperture arms please visit the store main page:
https://www.shapeways.com/shops/lensmounts
Follow this link to see the tutorial:
https://youtu.be/Jiv1HAlwF68