When I was a teenager, in the 70s, I always carried a penknife with a locking blade. It came in handy for gutting fish caught from the local canal, fixing my bicycle at the roadside, making skewers at BBQs (we used to have BBQs in fairly remote places!) and similar things. It was never used to harm or threaten anyone. Most of my friends also carried knives for the same reasons. It's not knives that worry me, but the apparent readiness of some young people to inflict serious injury or death on their peers. A knife amnesty like the current one is no more than window dressing, while the real problems go unchallenged.