An article is generally incorporated in every specification, or if omitted there, is included in the contract, stipulating that no extra work shall be paid for unless ordered in writing. The courts of the various states, view this condition in different lights, some holding that it is useless for parties to try to tie up by contract their freedom to deal with each other; while in other states, the courts refuse to admit parol evidence to establish a claim for extra work, holding them to the terms of the contract and requiring that written orders be produced on which to base the claims for compensation for the extra work performed. At the best, such a clause if not lived up to opens the door for expensive litigation, and as the proverbial ounce of prevention is worth a pound of cure, it is a wise policy to insist on written orders for all extra work, when ever a clause requiring such procedure is incorporated either in the specifications or contract. A good plan to pursue, one which will save after-disputes, as to the cost of extra work, and perhaps prevent expensive litigation, is to have a schedule of prices affixed to every specification or contract, stipulating just what each item entering into the makeup of a plumbing installation will cost, in case of extra work. This may take the form of a table or itemized list of all sizes of pipes, lead, wrought and cast iron, fittings of various sizes, oakum, lead, fixtures such as are called for in the original specification, labor, excavating per foot, etc. The cost of these various items has been already worked out and, after allowing the profit desired, the net costs to the owner can be stipulated so that he will know before hand what the extra work and materials will cost.