use the word combination
differently than it is used in a "combination lock." In
a mathematical combination, the
order in which an item occurs is not important.
Some old safes can be opened using more
than one combination.
disc lock consists of a sequence of discs
numbered on their outer edges. To open the lock, you turn
the discs (usually three) to the appropriate numbers.
Many apartment buildings, businesses, and
airports-even restrooms-use some form of keypad