From verso of the card: "A carpet or blanket should be fixed over the door opening . . . a flap being left to permit entry. This should be kept wet and at least twelve inches allowed to trail on the floor. . . . In addition, if there is a large crevice under the door, a wooden strip covered with felt should be nailed to the floor to make a gas-proof joint. The keyhole and all cracks must be stopped up."