For example, supermarkets, 4 groups of shelves are divided into several main frame, a few sub frame
The shelf and touch frame main sub frame: the main frame is the same distinction actually consists of two single column and cross beam is known with main frame, side frame connecting frame (follow-up constitute a single post and beam) and so on; also called a few lattice layers of several groups
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.
The main frame is a set of shelves that can be completely independent by the assembly of columns and beams.
