Article II, Section 2, Clause 3:
The President shall have Power to fill up all Vacancies that may happen during the Recess of the Senate, by granting Commissions which shall expire at the End of their next Session.
To be distinguished from the power to make recess appointments is the power of the President to make temporary or ad interim designations of officials to perform the duties of other absent officials. Usually such a situation is provided for in advance by a statute that designates the inferior officer who is to act in place of his immediate superior. But, in the absence of such a provision, both theory and practice concede the President the power to make the designation. 1