Immediately before the opening of the polls, an officer of election shall open the ballot containers in the presence of the political party or candidate representatives authorized to be present for the examination of voting equipment pursuant to § 24.2-639, if such representatives are available. The officers shall inspect the containers to ensure that they are empty, lock them, and deliver the key to one of the officers. One of the officers shall forthwith proclaim that the polls are open. The containers shall not be opened until the close of the polls and shall then be opened for the purpose of counting the ballots therein. The containers shall be kept in view of those voting within the polling place during the hours of the election.