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Alignment pins are cut in 4 quadrants and then the kerfs are closed up by bending the tabs that are formed by the cuts resulting in a tapered pin to ease assembly 

Emery cloth and filing is required to deburr the pin and smooth the surfaces 

Four holes in each end of the modules with the pins in the left hand holes of each pair of holes. When joined each modules is aligned with 4 pins making for a precise and rigid joint. Pin location is relative to the RAILHEAD'slocation so rails are brought to the edge of the module and are aligned to within thousandths of an inch