I believe a "needle" is a long piece of material, either steel or wood that goes through a structure to be used as a general support. And a "track" would be one that goes perpendicular to the first to form a grid.
But I could be wrong about the "track" definition.
I've seen slide shows before showing "needles" going through buildings, so I think I've got that one right....

Whatever you do, have fun doing it!