§ 121. Proposals. No contract shall be let, except after the receipt of sealed bids or proposals therefor, and no bids or proposals shall be received at any time other than at a regular meeting of said board, and unless they conform to the rules of the board and the general ordinances of the common council. All bids or proposals must be indorsed with the title of the work or materials to which they relate, the name of the bidder and his residence. It shall be the duty of each member of the board to be present at the time and place mentioned in the public notice for the receipt and opening of bids or proposals, and such meetings shall be open to the public. After all the bids or proposals have been presented, but not until one-half hour after the time stated in the public notice for holding the meeting, all bids or proposals shall be opened by some member of the board or by its secretary, publicly and in the presence of the bidders and other persons there present, and an abstract of all of such bids or proposals, with the prices and security offered, shall be transcribed in a book kept for that purpose, without any change, correction or addition whatever. A majority of the board need not be present when such bids or proposals are opened. The board may reject all bids or proposals received at any meeting and advertise again for new bids or proposals to be received at another meeting as above prescribed. No person submitting, or on whose behalf a bid or proposal is submitted, nor the principal or sureties on any bond or security accompanying the same, shall have the right to withdraw or cancel any such bid, proposal, or bond until the board shall have awarded the contract for which such bid or proposal is made, and such contract shall have been duly executed.