Which items on a purchase order are reserved for a customer?
In the goods-in screen (after you've clicked "Receive" for a purchase order or transfer), or in the purchase order lines screen (after you've clicked "Contents" on a purchase order or transfer), there is a button in the bottom-left corner. Clicking on this button will open a window showing all the customers who have ordered the items which are on this purchase order (or transfer):
This window will automatically open when you commit a purchase order or transfer into stock as well, to make sure you are aware of any customers who are waiting for the items you've just received:
Clicking on the contact link will allow you to view the customers' contact details, or send the customer an e-mail or text message.