Greetings ERPNext community 
I have been developing a provision for Putaway in ERPNext and would love to get your feedback on it. Before that, let’s understand its concept first.
What is Putaway ?
- Putaway is the process of assigning storage locations to stock that enters your Warehouse/Location.
- The stock arrives at your Warehouse/Location and you are suggested where to store it, automatically. You can look at it as the opposite of a Pick List.
- This is particularly useful when locations within a large Warehouse are tracked separately and each location has its own capacity.
- A Putaway strategy or rule forms the basis of this operation.
Where is this applicable in ERPNext ?
- Putaway Rules are applicable when you are receiving stock i.e. in Purchase Receipt and Stock Entry
- As of now Putaway is only applicable on the following Stock Entry types : Material Receipt and Material Transfer
How do I strategise Putaways in ERPNext ?
A Putaway strategy or rule forms the basis of this operation.
Keeping this in mind, ERPNext has a DocType called Putaway Rule.
- You can go over to Stock > Stock Transaction > Putaway Rule via desk or search for “Putaway Rule” in the awesomebar.
- Create a new rule that is recorded company-wise.
- You must set a capacity here. The UOM field is optional.
- You can also assign priorities to your rules, with the highest priority being 1.
- The rule is unique to each Item-Warehouse combination.
Now that you have created rules for your Items and Warehouse, the last step is applying the rule.
Wait, what Putaway strategy does ERPNext consider ?
- Here the strategy is purely based on Capacity and Priority.
- Warehouses will be auto assigned until they reach full capacity.
- Priority will be considered first. Followed by free space. When two rules have the same priority, the one with more free space available will be assigned.
- If you are running at full capacity (no free space in any Warehouse) you will be prompted the same.
How and where are these rules applied ?
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If you head over to a Purchase Receipt or Stock Entry (of type Material Receipt/Transfer) you will see a checkbox called ‘Apply Putaway Rule’
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After adding items to the Items table, you can check this checkbox and the Items will be auto-assigned to Warehouses based on your Putaway Rules.
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The rules are applied on Save as well if Apply Putaway Rule is enabled.
The Pull Request for this feature is open on Github. You can find a working GIF and explore some more features on the Pull Request.
Can I test it ?
Yes! You can pull this fork in your local instance and migrate your site.
If you don’t know what i said here 
or don’t want to do it, you can test it on the public site. Follow these steps:
- Go to the test site. Login with the credentials below.
- Email: test@erpnext.com
- Password: frappe123
Please feel free to give feedback in the thread below.
Edit: Login is more frictionless now.