A “board lot” is a number of shares traded as a unit. Different stocks have a different number of shares per board lot. For various reasons, the exchange may, in conjunction with the quoted company, alter the board lot size for particular stocks from time to time, for example, when heavy rights for capitalisation issues are made. To obtain the optimum price for both buying and selling, stocks should only be held and traded in board lots. Some stocks can only be traded in board lot form.