What do you mean by the main shelf and the shelf?
Straightforward, each row of shelves has only one main frame, and the others are racks. That is, a row of shelves is made up of 5 shelves, and then 1 main frames and 4 racks.
Each row of the shelves is arranged with a multi section shelf attached together, and when the shelf is connected, the first shelf and the second shelf can be shared between the columns, so there is a distinction between the main frame and the shelf.
The actual difference between the main frame and the rack is only a vertical column, and the other configurations are the same.
