Luggage locks

A bored cylindrical lock is one in which two holes are bored, perpendicular to one another, into the door. A large hole is bored into the door face and a smaller crossbore hole is bored into the door edge, as opposed to a mortise lock prep cut into the edge of the door. Typically, the face hole is sized from 1.5 inches to 2.125 inches (3.8 to 5.4 cm) and is centered at 2.375 inches or 2.75 inches (6.0 cm or 7.0 cm) from the leading edge of the door, this distance is referred to as the backset. Other, less popular, backsets are at 3.75 and 5 inches (9.5 and 12.7 cm). Residential doors are normally prepared for a 2.375 inch (6.0 cm) backset and commercial doors at a 2.75 inch (7 cm) backset.

History

The cylindrical lock was invented by Walter Schlage in 1909.

The bored cylindrical lock arose from a need for a more cost-effective method of locking doors. The previous norm, the mortise lock, is a more complex device, and its higher manufacturing cost as well as its more labor intensive installation make the bored cylindrical lock an ideal substitute, both in price and functionality.

Currently

The great majority of locks now in use on residences in North America are a variation of the cylindrical lock and are known as tubular chassis locks. Generally, they are not as strong as a cylindrical lock.

A lever tumbler lock is a type of lock that uses a set of levers to prevent the bolt from moving in the lock. In the simplest of these, lifting the tumbler above a certain height will allow the bolt to slide past.

‘Double acting’ Lever tumbler locks were invented in 1778 by Robert Barron of England. These required the lever to be lifted to a certain height by having a slot cut in the lever. So lifting the lever too far was as bad as not lifting the lever far enough. This is the type of lever lock most currently used today.

Lever locks generally use a bitted key. Some use a double-bitted key.

In computer science, non-strict two-phase locking, also 2PL, is a locking method used in concurrent systems.

The rules for 2PL are similar to those of Strict 2PL:

1. If a transaction T wants to read/write an object, it must request a shared/exclusive lock on the object.
2. A transaction cannot request additional locks on any object once it releases any lock, and it can release locks at any time (not only at commit time, as in Strict 2PL).

So, every transaction has a growing phase (it acquires locks) and a shrinking phase (it releases locks). 2PL allows only conflict serializable schedules, but doesn’t guarantee that deadlocks will be avoided.

2PL is one scheduling algorithm, sometimes used instead of:

• simultaneous locking, simultaneous release (Disadvantage: redundant locking, no interactive transactions)
• incremental locking, simultaneous release (Disadvantage: Deadlock)
• simultaneous locking, incremental release (Disadvantage: rollback, redundant locking)
• incremental locking, incremental release (Disadvantage: deadlock, rollback)

A bahut is a portable coffer or chest, with a rounded lid covered in leather, garnished with nails, once used for the transport of clothes or other personal luggage, it was, in short, the original portmanteau. This ancient receptacle, of which mention is made as early as the 14th century — its traditional form is still preserved in many varieties of the travelling trunk — sometimes had its leather covering richly ornamented, and occasionally its interior was divided into compartments; but whatever the details of its construction it was always readily portable. Towards the end of the 17th century the name fell into disuse, and was replaced by coffer, which probably accounts for its misuse by the French romantic writers of the early 19th century. They applied it to almost any antique sideboard, cupboard or wardrobe, and its use became hopelessly confused.

A warded lock (also called a ward lock) is a type of lock that uses a set of obstructions, or wards, to prevent the lock from opening unless the correct key is inserted. The correct key has notches or slots corresponding to the obstructions in the lock, allowing it to rotate freely inside the lock. Warded locks are commonly used in inexpensive padlocks, cabinet locks, and other low-security applications, since they are among the most easily circumvented by lock picking. A well-designed skeleton key can successfully open a wide variety of warded locks.

History

The warded lock is one of the most ancient lock designs still in modern use. It is thought to have been developed in ancient Rome.

Design

In the most basic warded lock, a set of obstructions, often consisting of concentric plates protruding outwards, blocks the rotation of a key not designed for that lock. Warded locks may have one simple ward, or many intricate wards with bends and complex protrusions; the principle remains the same. Unless the notches or slots in the key correspond to the wards in the lock, the key will strike an obstruction and will not turn.

A cylindrical post is typically located in the center of the lock. Its purpose is to provide a point of leverage for rotating the key, and to help correctly align the key with the wards. The key has a corresponding hole which fits over the post.

When the correct key is inserted, it will clear the wards and rotate about the center post. The key may then strike a lever, activating a latch or sliding bolt, or it may itself push against the latch or bolt. In a double action lever lock, the key may additionally push against a spring-loaded lever which holds the sliding bolt in place.

A tubular pin tumbler lock, also known as Ace lock or “axial pin tumbler lock” or “radial lock”, is a variety of pin tumbler lock in which 6-8 pins are arranged in a circular pattern, and the corresponding key is tubular or cylindrical in shape.

J.A. Blake is credited with patenting the first tubular lock in 1833. Walter R. Schlage continued the development of the tubular lock. He was awarded 11 patents, and his improvements made the tubular lock what it is today.

Tubular locks are commonly seen on bicycle locks, computer locks, and a variety of coin-operated devices such as vending machines and coin-operated washing machines.

Security

Tubular pin tumbler locks are generally considered to be safer and more resistant to picking than standard locks, though there are several ways to open them without a key. Even though the pins are exposed, making them superficially easier to pick, they are designed such that after all pins are manipulated to their shear line, once the plug is rotated 1/6 to 1/8 around, the pins will fall into the next pin’s hole, requiring re-picking to continue. As such, picking the lock without using a device to hold its pins in place once they reach their shear line requires over a dozen complete picks to unlock and relock.

Such locks can be picked by a special tubular lock pick with a minimum of effort in very little time; it is also possible to defeat them by drilling with a special “hole saw” drill bit. Standard tubular lock drill bit sizes are .375″ (9.53 mm) diameter and .394″ (10 mm) diameter.[1] To prevent drilling, many tubular locks have a middle pin made of hardened steel, or contain a ball bearing in the middle pin.

In 2004, videos circulating on the Internet demonstrated that some tubular pin tumbler locks could be easily opened with the shaft of an inexpensive ballpoint pen (e.g. BIC brand) of matching diameter. Trade website BikeBiz.com revealed that the weaknesses of the tubular pin tumbler mechanism had first been described in 1992 by UK journalist John Stuart Clark (see Kryptonite lock).

In Databases and Transaction processing, Two phase locking, (2PL) is a concurrency control locking protocol, mechanism, that guarantees Serializability. It is also the name of a class (set) of transaction schedules. Using locks that block processes, 2PL is subject to deadlocks that result from the mutual blocking of two transactions or more.

Two phase locking

According to the Two phase locking protocol, locks are handled by a transaction in two distinct, consecutive phases during the transaction’s execution:

Phase 1: Locks are acquired and no locks are released.

Phase 2: Locks are released and no locks are acquired.

The serializability property is guaranteed for a schedule with transactions that obey the protocol. The 2PL schedule class is defined as the class of all the schedules comprising transactions with data access orders that could be generated by the 2PL protocol.

Strict two phase locking

The Strict two phase locking (S2PL) class of schedules is the intersection of the 2PL class with the class of schedules possessing the Strictness property.

To comply with the S2PL protocol a transaction needs to comply with 2PL, and release its write (exclusive) locks only after it has ended, i.e., being either committed or aborted.

S2PL is a special case of 2PL, i.e., the S2PL class is a proper subclass of 2PL.

Strong strict two phase locking

To comply with the Strong strict two phase locking (SS2PL) protocol a transaction needs to comply with 2PL, and release both its write (exclusive) and read (shared) locks only after it has ended, i.e., being either committed or aborted.
A transaction obeying SS2PL can be viewed as having Phase 1 that lasts its entire execution duration, and no Phase 2 (or degenerate Phase 2). Thus, only one phase is actually left, and “two-phase” in the name seems to be still utilized due to the historical development of the concept from 2PL. The SS2PL property of a schedule is also called Rigorousness, and an SS2PL schedule is also called a Rigorous schedule.

SS2PL is a special case of S2PL, i.e., the SS2PL class of schedules is a proper subclass of S2PL (every SS2PL schedule is also an S2PL schedule, but S2PL schedules exist that are not SS2PL).

SS2PL is the concurrency control protocol of choice for most database systems since it provides besides serializability also Strictness, which is instrumental for efficient database recovery, and also Commitment ordering (CO) for participating in environments where a CO based Global serializability solution is employed.

In computer science, multiple granularity locking (MGL), sometimes called the John Rayner locking method, is a locking method used in database management systems (DBMS) and relational databases.

In MGL, locks are set on objects that contain other objects. MGL exploits the hierarchical nature of the contains relationship. For example, a database may have files, which contain pages, which further contain records. This can be thought of as a tree of objects, where each node contains its children. A lock locks a node and its descendants.

Multiple granularity locking is usually used with Non-strict two-phase locking to guarantee serializability. MGL uses lock escalation to determine granularity lock on a node and its ancestors.

Lock Modes

In addition to shared (S) locks and exclusive (X) locks from other locking schemes, like Strict two-phase locking, MGL also uses intention shared and intention exclusive locks. IS locks conflict with X locks, while IX locks conflict with S and X locks. The null lock (NL) is compatible with everything.

To lock a node in S (or X), MGL has the transaction locks all of its ancestors with IS (or IX), so if a transaction locks a node in S (or X), no other transaction can access its ancestors in X (or S and X).

MGL locking modes are compatible with each other as defined in the following matrix.

The Sault Locks (usually called the Soo Locks) allow ships to travel between Lake Superior and the lower Great Lakes. The locks are the busiest in the world, passing an average of 12,000 ships (”boats” in Great Lakes parlance) per year. This is achieved in spite of the locks being closed during the winter months, January through March, when ice shuts down shipping on the Great Lakes. The winter months are used to inspect and maintain the locks.

The locks bypass the rapids of the St. Marys River where the water falls 7 meters (21 feet) from Lake Superior. Sault Ste. Marie (pronounced Soo Saint Ma-ree) gives its name to both the Canadian and American cities at the site, in Ontario and Michigan, respectively. The Sault Ste. Marie International Bridge between the United States and Canada permits vehicular traffic to pass over the locks.

American locks

The American locks form part of a 1.6 mile (2.6 km) canal formally named the St. Marys Falls Ship Canal. They are owned and maintained by the United States Army Corps of Engineers. The first American locks were completed in May 1855.

• Davis Lock was built in 1914. It is 411 meters (1350 feet) long, 24 meters (80 feet) wide and 7 meters (23.1 feet) deep. The Davis lock is used rather infrequently to lock light freighters, tour boats, and small craft when traffic warrants. SS James A Farrell was the first vessel to lock through.

• Sabin Lock was built in 1919. It is 1350 feet long, 80 feet wide, and 23.1 feet deep. This lock is decommissioned and no longer used.

• MacArthur Lock was built in 1943. It is 244 meters (800 feet) long, 24 meters (80 feet) wide and 9 meters (31 feet) deep. This is large enough to handle ocean going vessels that must first pass through the smaller locks in the Welland Canal. First vessel through was the SS Carl D. Bradley.

• Poe Lock was re-built in 1968, after the Saint Lawrence Seaway had opened. It is 366 meters (1200 feet) long, 34 meters (110 feet) wide and 10 meters (32 feet) deep. It can take ships carrying 72,000 tons of cargo. The Poe is the only lock that can handle the large lakers used on the upper lakes.

There is a project, as yet unfunded, to built a new large lock to replace the Davis and Sabin locks.

Engineers Day

On the last Friday of every June, the public is allowed behind the security fence and cross the lock gates of the American Locks for the annual Engineers Day Open House.[1] Visitors are able to get close enough to the ships passing through the two operating locks to touch them.

Canadian locks

Canadian lock, the only lock on the Ontario side, was built in 1895. It broke down in 1987 and a new lock was built within the old lock. The lock was reopened in 1998 and is used for recreation and tour boats. It is 76 meters long, 16 meters wide and 3 meters deep.

The Sault locks are a well developed tourist site that offers viewing stands to watch the locks at work and tour boat trips through the locks. It is now designated a National Historic Site of Canada (see: Sault Ste. Marie Canal).

Saint Georges, Delaware is an unincorporated town situated on the Chesapeake and Delaware Canal in New Castle County, Delaware, about midway between the Delaware River and Chesapeake Bay.

The Chesapeake & Delaware Canal Bridge (Delaware Route 1) passes just west of town. It is the only cable-stayed bridge in the Delaware Valley and one of the first in the nation. It opened in 1995 as a replacement to the still standing St. Georges Bridge, which carries U.S. Highway 13 over the town of Saint Georges and the Canal. The St. Georges Bridge is in turn a replacement for a former lift bridge that sat in the middle of town. That bridge was knocked down in November 1939 when the German freighter Waukegan lost power and hit the south tower of the bridge causing it to collapse. Two people died that evening, the bridge tender and a sailor that was on the bridge of the ship at the time of the accident. One other bridge spanned the C & D Canal before the lift bridge. It was a small pedestrian swing bridge that crossed over the former Saint Georges Locks. It was destroyed when the locks were dismantled during the first widening and deepening (to sea level) of the canal.

Its ZIP Code is 19733.