 Crosses, also known as four-way fittings or cross branch lines, have one inlet and three outlets (or vice versa), and often have solvent-welded socket or female-threaded ends.Cross fittings may stress pipes as temperatures change, because they are at the center of four connection points.A tee is steadier than a cross; it behaves like a three-legged stool, and a cross behaves like a four-legged stool.