The low-profile, 300-gallon holding tank from T.S.F. is 16 inches tall, designed to easily slide beneath an RV or a field office. The placement of two 3-inch holes is standard: one in the corner for clean-out and easy access from the side of the trailer and another provided for the plumbing. Varied-size holes or spin welds can be installed anywhere in the tank for any application. They have been certified in the states that require certifications, require them by the truckload for temporary waste storage due to devastation, or are required to have aboveground tanks in campgrounds. 800-843-9286; www.tuff-jon.com.