The Edsal UR185P-BLK 5-shelf freestanding shelf unit has shelves made of particle board to support an 800 lb. per shelf capacity and a 4000 lb. total capacity when the weight is distributed evenly across all shelves. This unit has double-riveted beams that lock into double-rivet holes on the corner post for structural security. The corner post rivet holes on this unit are punched at 1-1/2 in. intervals for precise adjustment to desired shelf height. The steel rack has a black powder coat finish to resist corrosion. This unit is open on all 4 sides to facilitate access to shelf contents from any angle. The posts on this unit have a 2-piece design so it can be assembled vertically to create one 72 in. H x 36 in. W x 18 in. D unit or assembled horizontally to create two 36 in. x 36 in. x 18 in. units, 1 unit with 2 shelves and 1 unit with 3 shelves. (H is height, the vertical distance from lowest to highest point; W is width, the horizontal distance from left to right; D is depth, the horizontal distance from front to back.) This shelf unit has a rivet lock design for boltless assembly. Assembly instructions are included. A rubber mallet (sold separately) is recommended for assembly.