To make sure you are not carrying a knife that is illegal in your state, check out both the statues and caselaw of the state where you live. Although Chapter 46 of the Texas Penal Code states that:
6) "Illegal knife" means a:
(A) knife with a blade over five and one-half inches;
(B) hand instrument designed to cut or stab another by being thrown;
(C) dagger, including but not limited to a dirk, stiletto, and poniard;
(D) bowie knife;
(E) sword; or
(7) "Knife" means any bladed hand instrument that is capable of inflicting serious bodily injury or death by cutting or stabbing a person with the instrument
However, what fits into these categories is pretty much decided on a case by case basis. It is pretty much settled that any double edged knife is illegal to carry in Texas; some courts have found that a knife with a sharpened false edge on the top of the blade is a bowie knife. There has been little consistency is how different courts have interpreted this statutes. As stated, it clear you can't carry a knife with a blade length longer that 5.5 inches, or that's double edged, Unless you can show you use it for work, you can't carry an icepick. Some courts define Bowie knife by length, others by blade design.
Texas law says that in the absence of a specific definition, the common or everyday definition of a word will prevail.
My personal thought as an ex assistant district attorney and criminal defense lawyer in Texas, is don't carry a knife that looks like it's primary purpose is for fighting or inflicting harm on people. A Buck 110 is just as deadly, but nobody looks twice at it. If a knife looks like a tool, it'll probably be okay; if it looks like a weapon, you might have some 'splaining to do.
Also, it depends on the knowledge and mood of the cop as to whether you'll get in trouble for just carrying a questionable knife.