Interlake pallet racks feature stud-and-keyhole connections that get tighter as the load increases to improve strength over time. Interlock connections automatically set into the column, piston lock secures beam into place. The high-strength 15-gauge storage rack Beams are notched for roll-in Cross Bar. 13-gauge steel Welded Upright Frames are punched on 2 centers for easy beam adjustment and have a long-lasting baked-on enamel finish. The Starter Units include two upright frames and two pairs of beams. Add-On Units include one upright frame and two pairs of beams. Long-lasting baked-on enamel finish. Easy assembly.