The ones i've seen have folding blades. Though looking closer... they do seem to have some way to lock the blade in place.
There are a few different types I know of:
They all have edges under 3" but as far as I can see they are either fixed blades or locking folders. My opinion is that they all should require good reason. That said, most coppers couldn't care less unless you're waving it about in a drunken rage threatening to slice someone up!
Airport security can be a different matter, even though you will find the rules say you can take as hand luggage a
knife with a blade up to 6cm. The signs at baggage check in suggest that all knives are banned from being carried as hand luggage. Unfortunately many airport security staff appear to be poorly trained and believe this is law.
I have carried an old model Leatherman Kick multitool with a 2" (ish) non-locking blade (
with the blade "inside" the body of the tool) as hand luggage through security at quite a few UK airports. I tend to inform the baggage check in staff I have it in my laptop bag. On a few occasions they have claimed I cannot carry it onboard and I have pulled up the site linked to above. Most have accepted that this is the legal position and allowed me to carry it in most cases. Where not it has gone in to my hold luggage.
Some airlines have their own conditions of use which prohibit the carry of ANY bladed/sharp item as hold luggage, let alone hand luggage (yes, I am looking at you Easyjet!). That is their right (as stupid and overly cautious as it may be) and these days I avoid them where I can. If I can't avoid them the Leatherman goes straight in to my hold luggage.
That said, I have never been stopped from carrying my Leatherman Squirt on my keyring.