Depends upon your specific brand and model of mower, but generally, you have to disconnect the mower deck and slide in out from under the chassis. It is best if you have a diagram of the belt path from the manufacturer. Have you tried the maker of the mower through their web site? Some are rather simple, requiring no tools such as a Craftsman which I happened to change last Saturday. My Murray mower, however, requires a couple of basic tools to accomplish a belt replacement of the mower deck.