What Has Keys but Can't Open Locks?

The answer

A piano has keys, the black and white bars that are pressed to make a sound, and none of them fits a lock. Most pianos have 88 keys, 52 white and 36 black. The riddle uses the word "keys" for a second meaning, and the lock is only there to push the listener toward the wrong one.

Other things with keys but no lock

A piano is the usual answer, but a computer keyboard, an organ and an old typewriter also have keys that open nothing. A map has a key too, the box that explains its symbols. If someone gives one of these answers, it fits the riddle, though the piano is the one most people have in mind.

How the wording varies

Some tellers add the word "many" or "single" to stress how many keys there are.

• What has keys but can't open locks?
• What has keys but no locks?
• What has many keys but can't open a single lock?
• I have keys but open no doors. What am I?

An upright piano in 1903

Conundrums, Riddles and Puzzles (Dean Rivers, 1903) asks: "Which musical instrument is the most moral?" The answer is "An upright piano". The joke is that "upright" can mean honest as well as standing straight.