The padlocks manufactured by Abloy Security Locks use rotating detainer discs instead of springs to increase durability. A useful feature of the cylinder is that it can be removed from the lock body and rekeyed to a different combination for use in the same lock body. Medeco Security Locks, Inc. has padlocks with unique dual-locking characteristics that use pin tumblers that rotate and side-bar locking. Cylinders are available with restricted keyways and with the option of factory key control. The Best Lock Corporation provides a padlock with a standard key-removable core, which is interchangeable throughout the entire line of Best locks. This permits any type, size, or style of Best locks to be master-keyed into one system. The Model 19 is one of the Master Lock Company's finest padlocks. The body is made of laminated steel with a half-inch-diameter case-hardened alloy-steel shackle. Other quality padlocks are manufactured by the American Lock Company and Sargent and Greenleaf, Inc. A trailer king-pin lock is designed to lock onto the king pin of a semitrailer and provides an effective obstruction to prevent a truck tractor from coupling with the semitrailer king pin. King-pin locks are made by the Best Lock Corp., Transport Security, Inc., Otto Industries, A.L. Hansen Manufacturing Company, and B.M.R. Security Products Corp. Key control is crucial to the effectiveness of any lock. Key control should be under the tight supervision of a security professional.