Blanket PO's are used when you want to charge multiple purchases to the same PO. An example might be an open PO with an office supply store, a monthly bill that you track on a PO, etc.
To enter a blanket PO, follow the steps in Requisition Entry until you get to step 12. For a blanket PO, you will make the Quantity equal to the total amount in dollars you want the PO to be for. If you are doing a $5,000 PO, enter 5,000 for the Quantity. You would then enter 1 for the Unit Price. After that, continue with the Requisition Entry process from step 13.