When frisking a person for weapons, the police are attuned not only to the feel of possible weapons under clothing, but also to the feel of packaged drugs. Although a frisk may not turn up a weapon, it may turn up a suspicious package which the officer knows is commonly used to carry illegal drugs or some other illegal substance. This suspicion may turn into sufficient cause for a more intensive search of the person's clothing. The lesson here is that a frisk often leads to a legal search. And if a search produces an illegal substance, it may result in an arrest.