This tutorial is dated, if you are considering a CNC for your personal use, we would highly recommend purchasing a kit that is very stable from our wide range of machines available. After this video, the gantry will be fully supported with the bottom support and the y-axis serving as the top support. Isn't it nice that all of these parts are intrinsically related. The y-axis rail support will provide two functions. It's primary function is to serve as the rail for the z-axis assembly. The secondary, but really important function is to help support the gantry tighten around the cutting surface x-axis rail support.

First, you will need to measure the inside dimension of the gantry sides. Bring the sides closer together to provide a tight assembly, but not too much. Try to get the gantry sides as parallel as possible, it's not all that important, but it should be somewhat tight to appropriate support for the load of the gantry. Cut the y-axis rail support to the measured length. I'm using a router to cut the board. I would rather use a power saw, but I don't have one. I bought the router because I would need it for the CNC anyway. It's an expense my wife can justify... yeah right!