Immediately before the commencement of the poll, the presiding officer shall show the ballot box empty to such persons, if any, as are present in the polling station, so that they may see that it is empty, and shall then lock it up F1(if it has a lock) and place his seal on it in such a manner as to prevent its being opened without breaking the seal, and shall place it in his view for the receipt of ballot papers, and keep it so locked F2(if it has a lock) and sealed.