Racks are group of Locations organised into a physical rack. A rack has the following properties:
Rack index is a number that orders the racks into a picking route for order pickers within the warehouse.Aisle multiple racks are assigned into an aisle.Lock Locking a rack is a rare practice and has no functional use with the WMS at present.Locations are places within the warehouse where unit loads are stored. A location has the following properties:
Capacity the maximum number of unit loads that can be stored on this location.Max Weight the maximum gross weight that can be stored on this location.  We do not account for the additional weight of the storage container or pallet, only the gross weight of the goods.Location index a location index for ordering and creating a picking route.Last stock check The last date on which there was a successful (Accepted) stock take on this location.Location are ordered using the following scheme:
Picking locations are a pairing between a location and a stock code.   The max qty on a picking location is the the number of stock items that will fill the location.
Usually picking locations maintain a unit load with a count of the exact amount of stock; A free picking location has no unit load and no stock count.  
The stock count in a free picking location is counted by taking the difference between the stock on hand and the stock on unit loads.
Free picking locations are created by creating a picking location and setting the capacity of the location to 0 (zero). A Max Qty should be set to indicate how much stock can be stored in the location.
Note the capacity is set on the location it is not the same value as the max qty on picking locations.