A source document that production managers use to request materials for production and that is used to assign materials costs to specific jobs or to overhead is a:

materials requisition

Explanation:

materials requisition is type of form and slip used by production department of any firm. It is used to mention the quantity, units require to manufacture goods and  commodities. It used to keep paper record that how many items are ordered from inventory.

MATERIALS REQUISITION FORM.

Explanation: A materials requisition form can be defined as a document used by production managers in a production department of a company to request for materials used in the manufacturing process and also assign cost to the materials requested for.

The two major function of the material requisition form are;

1) recording the movement of materials throughout the manufacturing process.

2) allocation of production costs to goods in process