Frustrated with small patches to adjust live Z? If you have a self levelling bed you should be able to do all Z calibrations from one region of the printer bed. If that is the case why print another patch on the back of the bed when the front or middle will suffice?
I got frustrated when using individual small patches of 20x20 it only gave me two opportunities to see what I was doing before I had to move onto my next patch. A longer strip provides the opportunity to adjust live Z from one perspective and continue until you are satisfied with first layer thickness.
But perhaps you still need some room to see and adjust, so there is a series of small patches in a row included.
The serrations on the second strip gives prides a reference for turning the dial. And the strip is long enough to provide you ten minutes to get your first layer right. Hit the stop print button when you are happy....