Let's consider a company subcontracting the production of a product (clothing) to one subcontractor. Since the company does not always send the exact quantity (of tissues) to its subcontractor, we want to know the current stock available in the subcontractor. 

For example, a company can decide to send an entire roll of tissue instead of sending exactly what the subcontractor needs to create a clothing. 

1) We need to activate first of few setting: 

    Manufacturing - Configuration - Activate sub-contracting 

    Inventory - Configuration - Activate storage location 

These will create the location "Physical Locations/Subcontracting location". 

2) We will create a new location for our subcontractor (Inventory - Configuration - Locations) and we will select as a parent company the location mentioned here above ("Physical Locations/Subcontracting location"), for example : "Physical Locations/Subcontracting location/Subcontractor A". 

3) We need to assign this location to the contact form of the subcontractor. To do so, in you need to be in developer mode, go in Contacts, select the subcontractor and in the tab "Sales & Purchase" select as "Subcontractor location" the location we just created. 

4) In order to resupply at this location the subcontractor, we need to slightly adjust the route "Resupply Subcontractor on Order". To do so, go in Inventory - Configuration - Routes, select the route, select the follow rule: "Pull from - Physical Locations/Subcontracting Location" and modify the source location to "Physical Locations/Subcontracting location/Subcontractor Location A". Basically, we just precise the location of our subcontractor. 

5) Once products will be sent to the subcontractor, we will be able to have a view of the subcontractor's stock by going to Inventory - Reporting - Inventory Report and group by "Locations". 

Tips: We will also be able to register the quantity and the lot's number used by the subcontractor when receiving the subcontracted product. 

Tips 2: If we want our subcontractor to use first the available quantity on its location instead of sending automatically the needed quantity for one Purchase order. What we need to do is going to select the rule (mentioned before) of the route "Resupply Subcontractor on Order" and modify the field "Supply method" to "Take from stock, if unavailable, Trigger another rule". With this configuration Odoo will not create a resupply order, or will create one to compensate the possible lack of stock of the subcontractor, if the subcontractor have the needed stock for the purchase order.   

Tips 3: If we have multiple subcontractors, we need to create multiple locations (one for each subcontractor) and to create new rules in the route "Resupply Subcontractor on Order" (again, one for each subcontractor). 

Configuration of the products (for our example) 

- Subcontracted product, we obviously need a bill of material, to select our subcontractor in the BOM but also under the tab "Purchase", and the only route to tick is "Buy". We also need to set a reordering rule in order to trigger the demand. 

- Components: we need to set a supplier under the tab "Purchase" and to tick the routes "Buy" and "Resupply Subcontractor on Order". Reordering rules are not necessary, since the route creates automatically a "Resupply" on the Purchase Order.