Ich spreche ein bisschen Deutsch.

In the video, i think they use extruded aluminum as frame and square linear rail. From your previous post, you are using the extruded aluminum also as rail. Using extruded aluminum as rail is cheap, but not too much reliable, they need alot of maintain and calibration. About Round and Square Rail, you can check this website out, i think they have pretty much every information you need about those two. http://www.machinedesign.com/archive/round-or-square

Also check this out:


Hope these help.
Viele Grüße.