Tubular pin tumbler lock - Design. 1  The design of a tubular lock is similar to the pin tumbler lock, in that there are several stacks of pins. The key is a cylinder shape with notches cut around the outer or (rarely) inner edge. Each of these notches depresses a single pin inside the lock to a specific height allowing the lock cylinder to turn freely.
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The U.S. Postal Service allows customers to use the postcard rate for First-Class Mail for postcards that are at least 3.5 inches high by 5 inches wide but no more than 4.25 inches wide by 6 inches wide. As of April 2014, the postage rate for a postcard of this size is 34 cents. USPS also has a First-Class rate for large postcards that are no more than 6.125 inches high by 11.5 inches wide by 0.25 inches thick. These postcards cost 49 cents to mail as of April 2014. Learn more about Postal Services