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