Note: let's not discuss our opinions or feelings regarding these laws, I just want to know what the law actually is.

I'm heading back to NYC soon, for a brief visit. As far as the law is concerned, am I better off carrying a folding knife, a fixed blade, or a multitool with an OHO blade? Is there a length limit I should obey?

While I don't know myself, I believe that if you download the Knife Rights $1.99 Knife Rights LegalBlade™ App (for iPhone or Android), it will tell you what you need to know.

First off, thanks for noting the LegalBlade App availability. In asnwer to the OP's questions:

Note that New York City administrative code has an under-4-inch length limit and requires knives be carried concealed. Knife Rights recommends that you never carry your knife clipped to your pocket in New York City. Even when covered by a jacket, simply moving the jacket aside to get to a wallet has been enough to get folks arrested. Always ensure your knife is completely concealed at all times, including not "printing" on the outside of your clothing. In addition, be extremely circumspect about using a knife for any purpose in a public setting.

Note also that NYC has interpreted the state law against gravity knives such that if an officer can "wrist flick" the knife blade open and the knife blade locks open, that knife is an illegal gravity knife. NYC takes this position even if it requires multiple tries and use of exaggerated arm thrust or motion. Using this interpretation, most any lockblade knife might be deemed an illegal gravity knife.

A Swiss Army Knife, traditional slipjoint folder (Case, etc.) or something like a Spyderco Slipit if you want one-hand opening, all without a locking blade, cannot be considered an illegal gravity knife. And, of course, need to be carried completely concealed. If there's a pocket clip, take it off lest you by habit use it.

And, just to be clear, just because you cannot "wrist flick" open a lockblade folding knife does not mean a cop cannot. Trust me, they can and will. Since this is an arrest and go to jail offense, don't be stupid.

Added. BTW, just to make the point, I opened a Leatherman OHO blade in federal court: http://www.kniferights.org/index.php?option=com_content&task=view&id=373&Itemid=1

the current safe harbor is a non-locking non OHO blade. Like a typical SAK.

Thanks to all for the responses. I've put LegalBlade on my iPad and reviewed NY/NYC.

It seems like even an LM Wave is illegal even if fully concealed.

If it locks, it's best to avoid carrying it. I wouldn't count on some of the more esoteric locks (Opinal, Svord), or rescue hook blades to protect you against an unfavorable interpretation.

Also, considering what seems to be an increase in security theater, a padded and prepaid SASE would be a good thing to carry. I can't speak for the NYPD, but security guards are a capricious bunch.

P.S. Happy National Knife Day!

Can someone tell me what's the deal with locking blades? I know they don't like those in the UK either. I consider a lock a safety feature so you don't close the knife on your fingers. What is the "bad" interpretation of a lock that would lead people to want to ban them?

Lock + openable by inertia, centrifugal force, or gravity = gravity knife. A gravity knife is illegal.

The exact criteria for what constitutes opening inertia or centrifugal force is vague. It has been interpreted by the courts to include such techniques as as wild flailing of the arms, holding the knife by the blade (Spydie drop), and depressing the lock while swinging it. Under these criteria, a Buck 110 or a Spyderco Dragonfly is considered a gravity knife.

The only defense is to have a knife which does not lock open. E.G. Swiss army knives, traditional folders, etc. that have slip joints.

Just to make a few things clear. First off, this is essentially a New York City issue only, lest someone misunderstand.

Second, NY state's gravity knife statute does not include "inertia." It does include "lock," so a folder without a lock cannot be a gravity knife, hence the suggestion to avoid knives with locking blades.

Third, I am not aware of any NY court sanctioning "holding the knife by the blade (Spydie drop), and depressing the lock while swinging it" although we are aware of claims that arrests have been made by use of such techniques, they have not made it to court. The only technique that I am aware of that has gone to trial used a conventional arm and wrist motion to open the blade. Most of these arrests do not get to trial, although the cost to not get there can be considerable.

And, just to be clear, none of those extraordinary techniques are really necessary to open a Dragonfly, or even a Lady Bug, nor to open a Buck 110, both of the latter were demonstrated by us in Federal Court using conventional wrist and arm action only. It is a skill, however. One many cops in NYC have perfected.

Doug, can you explain what you mean by "common folding knives with a bias toward closure"? I've never heard that terminology before.