When the Enable inventory stock is enabled under store settings, users can register for products that are out of stock and be notified when the product is back in stock in the webstore. This feature is automatic with Znode.

Set the inventory and product from the admin to 0 with the Out-Of-Stock Options :

The webstore should display the following option if the Product is out of stock

Then the shopper will see an alert "You have successfully subscribed for receiving in-stock notification."