All new buildings should be made rat proof. When plans are being drawn for a building, the rat problem is frequently overlooked, usually because rats are not often present near sites selected for new structures. They are certain to come later, however, and should therefore be taken into account. Modern structures are so nearly rat proof that to make them completely so requires only slight and inexpensive changes. Furthermore, rat proofing is closely associated with fire stopping and with sanitary measures that are now required by law in many places. Cities in growing numbers have added rat proofing clauses to their building ordinances with such good effect that others are sure to follow their lead. Builders should therefore compare the cost of rat proofing during construction with the probable later cost, in case local laws should require that all buildings be made rat proof. RAT PROOFING FARM BUILDINGS The cost of rat proofing the entire premises of many American farms would amount to less than the loss occasioned by rats on the same farms during a single year. In no other place is rat proofing more badly needed or less often accomplished than on the farm. There are, however, numerous examples of rat-proof farms in nearly every county in the United States, and almost invariably they are the more prosperous farms, for the rat proofing of a farm is an indication that the farmer has learned the necessity of stopping all small leaks, which mean reduced profits. A rat-proof farm is not necessarily one in which the entire farmstead is absolutely proofed, but rather one where conditions are so unfavorable for any invading rats that they either will desert the premises of their own accord or may be easily routed by man or dogs. The source of the trouble on almost any heavily rat-infested farm can be traced directly to conditions that furnish rats safe refuges near abundant food. The commoner of these rat-breeding places are beneath wooden floors set a few inches off the ground in poultry houses, barns, stables, granaries, corncribs, and even residences; in piles of fuel wood, lumber, and refuse; in straw, hay, and manure piles that remain undisturbed for long periods beneath concrete floors without curtain walls; and inside double walls of buildings. In rat proofing the farmstead as a whole, attention should first be paid to the premises outside the buildings and later to each building separately. [Illustration: B31216 Figure 1.--An automatic garbage can, always closed]