Dont f**king do that, if you use a knife, your a willy. Guy at work hasa massive scar on his face from being stanley knifed. 2 blades in one knife, has like an inch wide scar go from his ear to his mouth.. Just smash them with the bike. I had 2 lads try an get mine when i was walking with it. tried to break my arm and my nose to get it, they didnt like. never even hit one of them, just pushed him over my bike an made him mad haha. carry a kubaton on your keys, f**king hurts when poked with one of them had some fanny try and take my bike when i was waiting at traffic lights to. 2 chavs on a bike, grabs my bars, elbow to his face and hes on the floor out cold. Defend yourself if you can, otherwise, get the hell out of there.