The Undertakers, before they shall be entitled to take any Rates in respect of the Harbour, Dock, or Pier, if required so to do by the Commissioners of Her Majesty's Customs, or at any Time thereafter when so required, shall erect on a suitable Spot within or near the Harbour, Dock, or Pier, to be approved of by the said Commissioners, and always thereafter maintain a Watch-house and Boat-house for the Use of the Tide Surveyors of the Customs and their Crew of such Size and Materials and in such Manner as shall be approved of by the said Commissioners, and shall also, to the Satisfaction of the said Commissioners, provide from Time to Time a sufficient Number of Huts for the Use of the Officers of Revenue, with all fit and necessary weighing Materials; and shall at all Times keep such Watch-house, Boat-house, Huts, and. weighing Materials in good and sufficient Repair.