Storage shelves, main frame and sub frame is how to distinguish?
Sub frame is the lack of an upright post, which needs to be attached to the main frame, and can not be connected to the shelves independently. If the 4 shelves are assembled into a column, then a "one master, three auxiliary" shelf combination form. Except that the first group needs two columns (main frame), others can share a column (auxiliary frame) with a group in front of it.
The main frame is a set of shelves that can be completely independent by the assembly of columns and beams
Main and subframe connection can save space and reduce cost. Solid performance is also stronger than single groups, so storage capacity is greatly improved. For example, two separate sets of storage shelves require four columns, but they can be combined into a single column, which requires only three columns to save an upright post. The more the number of connections, the more columns you save.
