The frame of my Prusa i3 Hephestos was a little shaky, so I wanted to find a way to reinforce it while changing as few parts as possible.
With only four printed parts, two 8mmx350mm steel or aluminum rods and some glue you can considerably improve your printing quality.
instructions:
Important: I designed this for a Prusa i3 Hephestos. So the distance between the corner part and the frame should be about 90mm for it to work.
EDIT: Added step-files for customization