Okay, finally nearing completion of my build after several issues and having to move house in the middle, but now I am stuck on a certain task. It is probably very simple it's just going over my head. I am referencing the build guide from this point and am wondering about the wording on the step where you measure the distance on one side (70mm in guide) and adjust to be the same on the other: "If there is any difference you can adjust it by holding one end in place and carefully moving the other end so they are both at the same distance. It may take a few goes to get it right. If you find it hard to adjust make sure the grubs on the pulleys are loose." What exactly are the "one end" and "other end" that it is referencing?