A bike rack is a device to which a bicycle can be securely attached to prevent theft. The rack is in turn anchored to the ground or a solid structure such as a building wall.
Early models tend to offer a means of securing one wheel: these can be a grooved piece of concrete in the ground, or a forked piece of metal into which a wheel of the bicycle is pushed. These are not very effective, since a thief need only detach the wheel in question from the bicycle to free the rest of the bicycle. They also do not offer much support, and a row of bicycles in this type of rack are succeptible to all being toppled in a 'domino effect'.
The more modern verion is known as the 'Sheffield', after Sheffield in England where they were pioneered. These consist of a thick metal bar shaped like a square arch. The top part is about level with the top bar of the bicycle frame, and thus supports the bicycle and allows the frame to be secured.
