Overlap spacing and approximate area calculations. We will see a model of roof type has a different first code number based on the manufacturer, but the codes follow it are similar. What does a number mean? such as TBR-760B. Code 760 mean 760 mm after overlapping, that is, we can use this number to calculate an approximate area, for example, constructing a warehouse with 8 meters wide and 10 meters deep with the roof sloping backwards. We have already known we must order 10-meter sheet but how many of them? We can calculate from the width which is 8 meters (8000 mm) then divide by 0.76 (from 760 mm). It will be equal to 10.52 sheets or 11 sheets.