Standard wire shelving features four steel poles, 7" to 8 feet in height, with shelves that are usually between 18 to 30 inches deep and two to six feet wide. The shelves have four holes on the corners where the poles insert and little plastic clips keep them connected. The shelves are held on by circular grooves on the poles which are usually spaced one inch apart throughout its length, making it extremely easy for the individual shelves to be moved to any height when the unit is fully assembled without taking apart the unit or moving the other shelves. No tools are required to assemble or disassemble these shelves, although a rubber mallet is useful.