This test is used to evaluate the strength of a backrest due to horizontal forces applied to the sample. The test applies to samples with backrest heights greater than 8 inches. The sample will be secured without inhibiting movement of the backrest. For backrests greater than 17.8 inches from the seat, the force will be applied 16 inches from the seat. For backrests less than 17.8 inches from the seat, the top of the loading device will be flush with the top of the backrest. The loading device will initially apply a force 90 degrees in relation to the backrest to all seating positions simultaneously. A load of 150 lb. per seating position will be applied first for one minute and then a load of 250 lb. per seating position will be applied for one minute.