Here is my Metric 3mm lasercut linear slide cut out of scrap acrylic. I honestly didn't expect it to actually work out well at all, it started as a sarcastic comment to a friend after you move it back and forth up the rail and break off any sharp bits and burrs it is practically friction less and as it has turned out quite the viable linear slide with a little bit of dry glide or something similar it may even offer quite a high service life *depending on the acrylic you use it may be required to shim two of the end bits with a bit of 80gsm paper.