It stands to reason that some system or order must be observed in taking off quantities, if confusion is to be avoided and every item entering into the makeup of the work included. For instance, if the plan of a floor be studied and an effort made to take off at one and the same time the various items of fixtures, water supply pipes, soil pipes, lead roughing and brass work on that floor, confusion will ensue and some of the items will be overlooked. A simple but effective plan to follow is to estimate separately the drainage system, the water supply system, fixtures, labor and general conditions. By such a course of procedure each subdivision of the work can be followed out from beginning to end and not an item overlooked.