As stated above this is for when you want to maintain vertical grain on the backs of your cabinets, you do get a warning that the back is greater than the sheet size when you process it, but i think Microvellum/Toolbox should be asking you if you want to split the back before you get to the processing stage. Also if you have adjustable shelves it would be good to add two rows of adjustable or continuous shelve holes into the centers of the two backs to support the shelve.