BEAMS EACH LEVEL REQUIRES FOUR. USE DOUBLE RIVET BEAMS ON TOP AND BOTTOM LEVELS OF ALL UNITS. USE SINGLE RIVET BEAMS ON ALL INTERMEDIATE LEVELS, OR INCREASE CAPACITY BY USING DOUBLE RIVET BEAMS ON ALL LEVELS. SAMPLE UNIT: HEAVY DUTY, 5 SHELF 48″ X 24″ ORDER; 6-48″ & 6-24″ SINGLE RIVET BEAMS, 4-UPRIGHTS, 4-48″ & 4-24″ DOUBLE RIVET BEAMS: EXTRA HEAVY DUTY, 5 SHELF, 48″ X 24″ ORDER; 4-UPRIGHTS, 10-48″ & 10-24″ DOUBLE RIVET BEAMS. BEAMS CAN BE USED AS LEDGES AT ANY REQUIRED HEIGHT TO PREVENT MERCHANDISE FROM FALLING OR ROLLING OFF SHELVES.