How do you keep weeds from growing inbetween bricks / blocks on a patio or walkway?

A brick walkway can't have the spaces sealed, or it will crack. So there's really no way to prevent weeds entirely. However, there are fairly easy ways to kill the weeds. One way involves flame, and I wouldn't touch that one with a ten-foot pole. But two others are herbicidal soaps, which have the additional benefit of cleaning your walkway, and potent vinegars, which are organic and should not damage anything but the weeds if used correctly. Sources: <a rel="nofollow" href="http://www.gardensalive.com/article.asp?ai=780&bhcd2=1180191943">http://www.gardensalive.com/article.asp?  more