Unfortunately, bathroom ventilation fans often are set up so that they exhaust air to the space between ceiling joists, especially if the bath is located on a lower level toward the middle of the house.
The United States Postal Service defines a postcard as: rectangular, at least 3 1â2 inches (88.9 mm) high Ã 5 inches (127 mm) long Ã 0.007 inches (0.178 mm) thick and no more than 4 1â4 inches (108 mm) high Ã 6 inches (152.4 mm) long Ã 0.016 inches (0.406 mm) thick.
Size 16 envelopes qualify as flats as do the catalog envelope sizes 1Â¾, 3, 6, 8, 9Â¾, 10Â½, 12Â½, 13Â½, 14Â½, 15, 15Â½. The flats postage rate would cover international envelope size C4 but not C3. All items that are not letters, postcards or flats are considered parcels by the USPS.