For the next two methods in the Sysudoku Order of Battle, we pause to load two template maps. The bv map is a 9 x 9 table on which we key in the contents of bv cells. The bv map later houses the XY Railway, a set of graphic curves along which every XY chain will lie. But first, the bv contents are copied, in one cut-and-paste operation, into the XYZ map, for the scan for XYZ wings, which I do first.
You might prefer to do these two scans in opposite order. The reason I don’t, is keep the easier, and more effective XY Railway scan from destroying XYZ-wings before I get to them.