Whenever, in the course of estimating, it becomes necessary for a contractor to resort to the architect to explain or make clear some provision in the drawings or specifications, such correction should be made immediately upon giving the explanation so the contractor will be justified in depending on the verbal instructions the architect gives him. For instance, the labor of excavating for the plumbing pipes is sometimes specified in the general specifications as part of the mason's work, and in the plumbing specifications as part of the plumber's work. Likewise, the cutting and patching throughout the building is sometimes included in both the carpenter's and the plumber's specifications.

If, in such a case, the plumbing contractor asks for information as to who shall do the digging, cutting and repairing, and is told that such work will be done by the mason and carpenter contractors respectively, but no change is made in the plumbing specifications by crossing out the section making it the plumber's duty to do such work, the plumbing contractor, to protect his own interests, must estimate on doing the work, as he can be held to perform it in case he signs a contract to furnish all materials and perform all labor according to the plans and specifications. The only course for the architect to pursue in such a case is to decide immediately the matter is called to his attention, and cross the provision or requirement out of one specification, leaving it in the specification where it rightly belongs.