Prusa i3 frame connector
No more trouble with the washers when attaching the y-axis carriage to the Prusa3 frame.
Put them in between the washers on the long y-axis threaded rods. It will help you attaching and tightening the frame while keeping each washer on its side. This part is designed for 6mm thick frame. Mine is acrylic but it will work equally well on an aluminium frame.