Wood preservatives are generally grouped into two categories: preservatives used for in-place field (remedial) treatment and preservatives used for pressure treatments. A limitation of in-place treatments is that they cannot be forced deeply into the wood under pressure. However, they can be applied into the center of large wooden members via treatment holes. These preservatives may be available as liquids, rods, or pastes. Pressure-treated wood has much deeper and more uniform preservative penetration than wood treated with other methods. The type of pressure-treated wood is often dependent on the requirements of the specific application. To guide selection of pressure-treated wood, the American Wood Protection Association developed Use Category System standards. Other preservative characteristics, such as color, odor, and surface oiliness may also be relevant. Guidelines for selection and application of field treatments and for selection and specification of pressure-treated wood are provided in this document.