27 C.F.R. § 26.199a
(b) Sealing bulk conveyances. When a shipment is made in a tank, van, or other bulk conveyance (other than barrels, drums, or similar packages that are not containerized), all openings affording access to the spirits shall be sealed by the Puerto Rican revenue agent is such manner as will prevent unauthorized removal of spirits without detection.
(Approved by the Office of Management and Budget under control number 1512-0250)
[T.D. ATF-198, 50 FR 8551, Mar. 1, 1985. Redesignated and amended by T.D. ATF-459, 66 FR 38550, 38551, July 25, 2001]