Troops in Vietnam sometimes used a B unit ration can as a field expedient stove to heat their C-Ration meals. Air holes were punctured in the empty can and a Trioxane fuel tablet, or a pinch of C-4 plastic explosive or sand saturated with gasoline was used as fuel.
The Lightweight Grid was developed by the Land Warfare Laboratory as a means of supporting the ration can above this field expedient stove. It weighed just one ounce and consisted of two steel rectangles (3-7/16 inches x 1-5/16 inches), which slotted together into a X configuration. It was intended that the grid would be used for at least three meals before being discarded.
Tests by personnel at the Land Warfare Lab and by the 82nd Airborne Division at Fort Bragg in November 1970 were generally positive, but suggested that the grid height be halved to bring the food closer to the flame. An informal evaluation by Ranger trainees found the canteen cup to be unstable on the grid. The Lightweight Grid was also tested by the 8th Army in Korea in 1971.1
1. Improved Ration Heater And Fuel Tablet - Interim Report (U.S. Army Land Warfare Laboratory August 1971)