44 CFR §333.33

1. (a)Set-aside. A set-aside is an official action that requires a person to reserve materials, services, or facilities capacity in anticipation of the receipt of rated orders.
2. (b)Directive. A directive is an official action that requires a person to take or refrain from taking certain actions in accordance with its provisions. For example, a directive can require a person to: Stop or reduce production of an item; prohibit the use of selected materials, services, or facilities; or divert the use of materials, services, or facilities from one purpose to another.
3. (c)Allotment. An allotment is an official action that specifies the maximum quantity of a material, service, or facility authorized for a specific use to promote the national defense.