Main Page | See live article | Alphabetical index A chain tool is a small mechanical device used to break a bicycle drive chain in such a way that it could be mended with the same tool. A bicycle chain has links that are pinned together. These pins can be pushed out with the chain tool. The pin is not totally removed because it would be very difficult to mend the chain if it were loose. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.