(a)The issue of materials to contractors who have contracted for completed items of work is generally permissible only in the following circumstances:-(i)when, under the operation of Rule 241, it is necessary to retain in the hands of Government the supply of imported materials, and(ii)when, in the interest of work, or with the object of utilising existing stocks of materials, it is desirable to retain in the hands of Government the supply of certain other materials as well, and a condition to this effect has been inserted in the contract.