By request these are the three pieces i designed for making a stepper-motor adjustable laser bed for the K40 laser.
These are specifically designed for use with: - A 12x12mm wood rod, which you can saw to size. I found this at the local hardware store. - 3 or 4 pieces of 8mm diameter lead screw (length about 100mm), with the accompanying nuts. I found these at Aliexpress, search for "T8 leadscrew 100mm"
There's a decent tolerance between the 12mm rod and the holes it fits into. You will need some glue to put the thing together.
Use 2 corners for screws, 2 corners without screws, and 1 sidepiece if you're going for 3 lead screws. Three points define a plane, so i recommend this one for the most consistent result. However, most of the world thinks a rectangular bed should be supported on all four corners, even though adjusting one corner incorrectly will lead to a warped, non-flat surface. If you prefer this method, just print 4 times the corners with screw holes and forget about the other models.
I connected the nuts to the printed parts using small tiewraps, though you could use small bolts as well.
I have automated this whole setup using 3 stepper motors connected to the bottom of the K40, and an arduino to control them, but you can just use this as a manual bed, by turning the lead screws by hand.