Ian Dorriety, age 15, of Haggerstown, Md., for his question:

WHO INVENTED THE YALE LOCK?

An American inventor named Linus Yale Jr. came up with the idea for the Yale lock in 1865. The idea was based on a principle similar to that of the ancient Egyptian lock. This invention was the pin tumbler cylinder lock, which today is still the most secure key operated locking device known to man.

Within the case of the pin tumbler cylinder lock is a series of pins and drivers that extend vertically through the cylinder and into an inner plug. Only the correct key raises the pins and drivers so that the breaks between them are lined up with the joint between the cylinder and its pins.

When precisely set up, a key can rotate the plug to activate a bolt or latch. A minute variation from the proper height of any pin prevents the key from being turned.

In addition to being important because it provides a degree of security that can't be found with any other kind of key operated lock, the pin tumbler cylinder lock was the first to be ideally suited to mass production.