I only use this for the top drawer of my ALEX Drawer Unit, where I have all the tools I regularly use. It is much more fun when you always have all the tools at hand and do not have to constantly rummage for them.
You can scale the rails in your slicer to the length you need. The measuring is kind of tricky! You have to consider the thickness of the joints very carefully. I made a few mistakes at measuring so I had to throw away some rails that didn't fit.
I recommend you to not print all rails at once, but to only print 1 or 2 and then try out if they fit together with the joints. Depending on your printer it's may be also necessary to scale the thickness of the rails a bit to get a perfect fit with the joints. So first print the joints, then the rails.
You can find the sliding top tray, shown on the second picture here:
https://www.thingiverse.com/thing:5580380
Estep
