Recently, I got this steel frame to build kind of a neo-retro road bike) out of it. The frame has this perverse S-shaped seat tube. It looks cool but places the front derailleur too high and forward resulting in the chain rubbing against the bottom of the cage. I designed this little spacer that goes between the derailleur and the frame to move the derailleur back and down and to rotate it a few degrees - effectively rotating it around the cranks’ axis.