This clear spacer goes in the space between the sword rail and the lock guard. It separates the balls from the metal where they sit in the lock. This spacer breaks any magnetic circuit, and eliminates ball jams caused by magnetized balls.
This part is particularly important if you are using chrome steel balls.
We have reports that magnetic balls also jam in the Stern trough, so we are looking at that.
Installation Instructions Pictures click here: http://mrtn.smugmug.com/Other/2010-04-27/11986523_HupH8#850175938_z3ZSu