The plumbing contractor should keep a cost book, properly indexed, in which to note the latest quotations on materials received by him. Plumbing supply houses send out from time to time new discount sheets, letters telling of changes in discount from the last quoted, and notices that new fixtures or goods have been added to the line carried, or that the manufacture of some fixture listed has been discontinued; as soon as these various notices are received they should be immediately noted in their proper places. If the manufacture of certain goods is discontinued, that information should be posted in the catalogue where the goods are illustrated and described. If new fixtures are added to a manufacturer's line the illustrations and descriptions should be entered in the catalogue and properly indexed so that they can be easily located. Should the list price on any goods be altered the list price in the catalogue should be changed to conform to the new quotation. If these precautions are not taken the contractor will find to his cost that he is estimating on old prices, and either failing to secure the work or contracting for it at a loss, according to the condition of the market since he last corrected his catalogues. Again, he might be estimating on fixtures which are no longer made, or, when limited for time, guessing at the cost of some new fixture he knows nothing of because he has not properly entered it in its proper catalogue.

The cost book is solely for the purpose of keeping account of the latest discounts quoted, which should be entered as soon as received. Putting off until some future time is liable to be putting off forever, and depending on memory is extremely uncertain.

The list and discount on stock goods, such as soil pipe and fittings and wrought pipe and fittings, should be carried in mind, but never depended upon when estimating a large operation.

Oftentimes, while inspecting the work in a new installation, the contractor is called upon to quote a price on an extra sink, water closet or lavatory, and if he has the cost of all material required in his mind, or a memorandum of prices in a pocketbook, he can quote a price on the spot and probably close the order immediately, while if time were required to look up prices, the owner might change his mind.