Well, taking the above mentioned cautions into account, I would like to add my 2 cents.
I have lived in Maryland my whole life, have more knives and sword around my house than I can actually count, and I have obsessively researched the law to the point of conducting interviews with cops and lawyers from around the state and even diving into court transcripts. (I read a lot of other state laws too, but I live here so of course it's going to get priority).
The state of Maryland only has two knife laws,
Criminal Code 4-101 and 4-105. 4-105 defines and prohibits
sale of switchblades, but has no other effect.
4-101 says it is illegal to carry a dangerous weapon concealed, but names "penknives" as exempt. Penknives are not defined in the law, but they are defined by multiple binding court decisions as
any knife where the blade folds into it's handle, no matter how large it is. Because they are
exempt from 4-101, you can carry them however you damn well please, completely hidden or in full view. Disregard any BS you hear about having the clip showing. This is set in stone, no matter what any cop tells you. In 2002 a cop ending up losing his badge because he was ignorant that folders were exempt; the man he inappropriately arrested took him to federal court, and won. Twice. You can read it here right from the horse's mouth:
http://www.ca4.uscourts.gov/Opinions/Unpublished/011565.U.pdf
Fixed blades are the funny part. It's a gray area. 4-101 names "dirk knife" and "bowie knife" as dangerous weapons (thus, illegal to conceal, but legal to open-carry), but it doesn't define them nor is the statute limited to them. Because of this, cops tend to lump all fixed blades under these terms, so any time you are carrying an FB fully concealed from view, you are at risk of arrest if you happen to piss some cop off enough that he's going through you're stuff. Mind, arrest does not equal a conviction. In State v Hutton, the court threw out a concealed weapon charge against a man because his knives were work tools and were of a non-threatening design (
Boye Basics). They never even went to trial. But he was lucky, I would not take that risk myself, and keep any fixed blade I carry visible on by belt or attached to my backpack strap.
As for NY, I don't touch that.