I personally have never seen one with a good functional lock for the closed position. I say "functional", because in my mind it would have to be able to be released in the same motion as opening the blade, otherwise it would be too cumbersome to be effective in an emergency or self defense situation. I carry a Kershaw Leek as my edc knife, and have for about 10 years now. In that time I have never had it open in my pocket, or accidentally at all. There is a lock, but it holds the tip of the blade, which I find cumbersome and useless to employ one handed, so I tightened the screw so that it can not accidentally lock the blade, but I never actually use it either. For those talking about something else to go wrong, I once felt that way, but this Speed safe mechanism has me sold on it's durability as I have had several over the years in all conditions and never once has any of them failed me. If it did break, then the knife would still function as a regular one hand opening knife, so I don't see you have anything to lose even if the spring breaks.