A pneumatic closing apparatus suitable for metering grain or other material gravity discharged by twin pendulum hopper doors from a hopper trailer. The laser amplifier module also includes a second amplifier head disposed along the optical amplification path adjacent a second end of the enclosure and a cavity mirror disposed along the optical amplification path. A pH builder is added and following mixing primary and secondary froths are recovered. The external natural gas purge results in a cleaner bed before the start of each adsorption cycle. The contouring sanding pad is versatile in its various forms, shapes, sizes, and adaptability.