The riddle
What Has a Foot but No Legs?
The foot a snail walks on
Snails have a foot and no legs. Britannica says the foot is the organ of movement in land snails, which glide along on waves of muscle contraction that run along the underside. The snail group is called gastropods, and the word comes from Greek words for stomach and foot, so the foot is built into the name. Slugs are gastropods too, and they get around the same way, on a single muscular foot, with the shell reduced or missing.
A ruler is the other common answer
Many tellers give a ruler, because a common school ruler is a foot long and has no legs. That answer may well be given more often than the snail, and both fit the wording. A foot is 12 inches, which is 30.48 centimeters, and the international foot has been defined as exactly 0.3048 meters since 1959, according to the National Institute of Standards and Technology.
Why the snail still earns its place
The ruler is a measuring joke and the snail is a real animal, so they sit at opposite ends of the same pun. A snail does not use its foot to stand. It uses the foot to travel, and the whole body rides on it. Gardeners often spot where one has been by the shiny trail it leaves behind. Telling the riddle with the snail makes a good moment to show a picture or a real one in a garden.
Two feet, one question
The word foot names a body part, the muscular underside of a snail and a unit of length, and the riddle can lean on any of the three.