Batching equipment may be either stationary or portable and creates either a wet or dry material. Wet material is used in ready mix operations and plants that use high-slump concrete. Dry material is used for products such as pipe, block or pavers, which can stand on their own almost immediately after batching. An important factor in training operators to use batching equipment is the end product. It is easier to train a worker who already knows concrete than one who doesn't. Learning to operate the computer that controls the batching equipment may be the most difficult job for some operators who are unaccustomed to computers. Aggregate moisture content must be taken into consideration when batching, because water suspended in the aggregate will affect the water-cement ratio in the final mix. For this reason, electronic probes should be employed to determine the water content of aggregate. Dryers can also be used to maintain specific moisture content. Proper maintenance is essential to the prolonged life of batching equipment. With the responsibility to maintenance also comes the responsibility for safety. Proper lockout/tagout procedures must be followed, as well as other simple guidelines to ensure worker safety during maintenance procedures.