Abstract: In a storage system comprising rows of shelves defining lanes for the storage of cartons or pallet loads and like wherein the shelf lanes are adapted to receive inventory loads one behind the other, a push-pack system comprising a pair of track adapted for wheels to roll upon the inner and outer edges of the top surface thereof, a first cart with a rectangular frame with wheels to ride on one edge of the tracks, a second cart having a U-shaped frame adapted to receive the first cart nested within the frame at approximately the same elevation and having wheels to ride upon the other edges of the track. Variations may provide for three or four carts providing storage of loads four or five pallets deep.