One method for repeating structure is to create and debug one structure, then copy and replicate that structure as many times as needed. However, this can lead to complex diagrams and hard-wiring of constant values and number of structures. A better way to repeat structure is to use subscripts. A subscript is created and added to the one original structure, creating as many structures as there are subscript elements. Now numbers of structures and numerical values for all structures can easily be changed.
Diagrams are also neater.
A retail outlet such as a shoe retailer might have stores in three locations. A model can be built for one store with structure for staff, inventory, sales, etc. Once that model simulates properly, a subscript is created called Location, with the subscript elements Boston, New York, and San Francisco. The subscript Location is added to the one store structure, constants are modified to reflect the value for each location, and now the one model contains three structures. Each subscripted structure can be individually customized, with different constants, multiple equations, even multiple subscripts.