I love my RepRack--it lets me have 8 linear feet of storage up above my closet doors, making use of space that would otherwise be wasted.  However, I live in Southern California where we occasionally have earthquakes.  While we all fear "The Big One", most of the jolts we get are minor.  Those smaller quakes will easily knock things off of shelves.  If my filament rolls are shaken of the rails there will be a lot of damage and/or injury to whatever or whoever is below, and I'd like to avoid that.

In other words: I know it's impossible to protect against "The Big One", but it would be a shame not to protect against the more common small tremors.  With that in mind, my addition to the RepRack system is a Hanger Lock, intended to keep the hangers (and rails) from coming out of the wall cleats.  It fits in the space between the hanger and the cleat, keeping the hanger in place.

The Hanger Lock might also be useful to anyone who has their RepRack in a location where someone could bump into it.

Installation is pretty simple.  First press the left half of the lock thru the hanger/cleat gap first, making sure it is fully inserted.  Then, press the right half thru.  Finally, use a 20mm M3 hex socket screw to secure the two halves to together.  (You can use a shorter screw, down to around 10mm, in a pinch).

I printed my parts using PETG with increased perimeters, although this is probably overkill.

You may be thinking "I'm glad my hangers and rails are now secure, but how do I keep the filament from shaking off the rail?"  Great question!  The short answer is "Hook and loop straps, aka Velcro".  I go into more detail with this design, which includes some nifty 3d printed filament tags.

I've included both the .stl file and the Fusion 360 design for the hanger lock.

Please let me know if you found this design useful.  Thanks for reading!