Master Lock No 140

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Master Lock No. 140

Master Lock No. 140
Name Master Lock No. 140
Manufacturer Master Lock
Lock Type Padlock
Lock Design Pin-tumbler
# of Components 4
Component Type Pin-tumbler
Related Locks
Master Lock No 141
Master Lock No 142

The No. 140 is a pin-tumbler padlock made by Master Lock. The No. 140 is a 40mm wide solid body padlock with an inner cylinder that uses four pin stacks and may contain spooled security pins. The shackle has a diameter of 6mm, and a length of either 22mm or 38mm.

Principles of operation

The No. 140 cylinder is a pin-tumbler lock with four pin stacks. Older versions of the lock use one spool pin in the third chamber, more recent versions may have the spool in a random position or no spool at all. The No. 140 can only be opened by rotating the plug clockwise.

See also Pin-tumbler (Principles of Operation)

Disassembly instructions

The No. 140 cannot be disassembled non-destructively; to disassemble it the lock must be sawed in half. The lock is nonfunctional once disassembled because the padlock body acts as the cylinder for the lock.


The 140s low pin-tumbler count and poor manufacturing tolerances allows it to be easily picked by low skill attackers despite having spool pins. It is commonly used in locksport groups as an introductory lock for beginners to learn about defeating security pins (although note that some recent examples have no security pins at all).

The 140 series is vulnerable to overlift attacks, where the entire pin stack can be lifted with a comb pick into the driver's pin chamber, allowing plug rotation.

The No. 140 may be vulnerable to one or more of the following:


See also