i agree with what slaam said. I've gone hiking in malaysia and carried a utility knife across the woodlands checkpoint. Customs officer asked me what was I doing with that knife on my return. I told him I just came back from a hike in malaysia. He asked a few other questions, checked my other items (including stinking clothes) and i got through.
Another incident was while returning from a dive trip from malaysia. My instructors had diving knives with them and they didn't have problem getting through customs.