The ceiling, inside walls, and floor of said room must be constructed of brick, stone, or tongue-and-groove planks. If there are windows in the room the same must be secured by gratings or iron bars, and to each window must be affixed solid shutters of wood or iron, constructed in such manner that they may be securely barred and fastened on the inside. The door must be substantial, and must be so constructed that it can be securely locked and fastened. SEC. 5. At least two sets of tanks or receptacles for storing de-naturing material must be provided, and each set of tanks must be of sufficient capacity in the aggregate to hold the de-naturing material which it is estimated the distiller will use for thirty days. A set of tanks shall consist of one or more tanks for storing methyl alcohol, and one or more tanks of smaller capacity for storing other de-naturing materials. The capacity of each tank must be ascertained and marked in legible figures on the outside. The tanks must not be connected with each other, and must be so constructed as to leave at least 18 inches of open space between the top of the tank and ceiling, the bottom of the tank and the floor, and the sides of the tank and walls of the de-naturing material room. Each tank shall be given a number,and this number must be marked upon it. There shall be no opening at the top except such as may be necessary for dumping the de-naturing material into the tank and thoroughly plunging or mixing the same. Said opening must be covered so that it may be locked. Likewise the faucet through which the de-naturing material is drawn must be so arranged that it can be locked. Each tank must be supplied with a graduated glass gauge whereby the contents of the tank will always be shown." CUSTODY OF DE-NATURING BONDED WAREHOUSE. "SEC. 6. The de-naturing bonded warehouse shall be under the control of the collector of the district and shall be in the joint custody of a storekeeper, storekeeper-gauger, or other designated official and the distiller. No one shall be permitted to enter the warehouse except in the presence of said officer, and the warehouse and room shall be kept closed and the doors, exterior and interior, securely locked except when some work incidental to the process of de-naturing and storing material is being carried on. Standard Sleight locks shall be used for locking the de-naturing bonded ware-house and the de-naturing material room, and they shall be sealed in the same manner and with the same kind of seals as distillery bonded warehouses and cistern rooms are now sealed. Miller locks shall be used in securing the faucets and openings of the mixing tanks and the de-naturing material tanks. The officer in charge of the de-naturing bonded warehouse, material room, and tanks shall carry the keys to same, and under no circumstances are said keys to be intrusted to anyone except another officer who is duly authorized to receive them."