An illegal knife is defined as any of the following by TPC 46.01(6):
"Illegal knife" means a:
(A) knife with a blade over five and one-half inches; (The blade is technically only the sharpened edge, but many LEOs consider the "kick", or the unsharpened area between the edge and crosshilt/handle, as part of the blade. Most illegal knives are illegal because they fall into this category)
(B) hand instrument designed to cut or stab another by being thrown; (These are your hand darts, your shurikens and throwing stars, and any knife balanced for throwing)
(C) dagger, including but not limited to a dirk, stiletto, and poniard; (The general key here is "no double-edged knives")
(D) bowie knife; (A Bowie is generally too long and a true Bowie is balanced for throwing, but shorter unbalanced variations exist; they were specifically banned because of their iconic popularity in Texas)
(E) sword; (this includes cane swords and katanas)
(F) spear; (this includes canes with a knife in one end)
A "knife" can be manufactured or improvised, as subsection 7 states:
"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.
Any "shank", from a piece of glass or plexi to a sharpened length of rebar is a "knife". Similarly, hand saws, scrapers, straight razors, and box cutters are knives.
In addition, switchblades are also illegal knives, and are defined as the following:
"Switchblade knife" means any knife that has a blade that folds, closes, or retracts into the handle or sheath, and that:
(A) opens automatically by pressure applied to a button or other device located on the handle; or
(B) opens or releases a blade from the handle or sheath by the force of gravity or by the application of centrifugal force.
Two big keys here:
* It is NOT a switchblade if, in order to open the knife, pressure must be applied to the blade. This means "spring-assisted" knives are legal in Texas. Utility knives, though they do have a "button", do not open "automatically" as per the definition; the button allows the user to slide the blade out by the amount the button is moved.
* However, practically any knife designed to be opened with one hand can be made to open by a flip of the wrist without touching the blade. This means pretty much any knife with a thumb stud, hole, or other opening device facitating fast deployment can get you in trouble with a cop looking for an excuse to haul you in.
It should be noted that the illegality of those knives in Texas relates only to the carry of such knives in public. They are legal to possess; you can buy them, transport them to and from places that lawfully trade in them, keep them in your home collection, and even use them around your home, but you cannot put one in your pocket and walk around a mall.
