Originally Posted by MNBiker

If you must leave your bike for a few minutes without locking it, there are a few other methods for slowing down any would-be thief: As already mentioned, put it in the lowest or highest gear; lay the bike on the ground so they can't so quickly take off; disconnect or loosen the brake cables at the calipers if it is easy -- although I would hate for a thief to get killed in traffic for just the sake of a bike; or take the chain off the chainring.