My understanding for years has been that knives of less than 4" length were permissible carry-on. For a couple of decades, I have been carrying a mini-knife, which is 3" total length, with a blade that protrudes 0.5" (yes, half an inch). Sort of a tiny exacto knife with one blade. Before I ever started carrying it, I checked and was told (once the laughter died down) that it hardly qualified as a dangerous weapon. I have carried it through at least 40 airports in Canada, the US, and internationally, and it has often been examined and then put back in the little pass-through tray, often with the comment that it's a neat/useful little item.
At our beloved Pearson airport las Friday, I was informed that it was a restricted item because it had a sharper blade than a knife and was therefore not covered under the 4" knife rule! Same response from 2 levels of supervisors. I either had to let them confiscate the blade or go back to the airline counter, stand in line, ask for this humungous blade to be checked through, and then stand in line to go through security again. So, I am looking for something in print that defines what permissible. Denying me access on the basis that I am carrying a dangerous weapon for a tiny knife with a 1/2 inch blade is akin to getting a speeding ticket for going 50.1 mph in a 50 zone. A ballpoint pen would be a more dangerous weapon than what they took from me.
I am all for security, but I am also all for common sense and consistency of application of the rules. First, though, I'd like to know exactly what the rules say with respect to sharp/cutting objects.