Would it be illegal to carry a knife in the car?
Carrying a knife with your or in your car as a tool or instrument shouldn't be against the law; but it can be sometimes confusing.
After doing some research we found some information about this too: States usually have a limit on the size of blade, and I'm pretty sure they don't allow ones 7" long. If it is sheathed in a proper holder and not hidden then you might have a cop that is understanding. That is as long as you inform him/her about it before they begin a search or if they ask you if you have any weapons in the car. However, if you live in Dallas, Austin, or Houston then you will probably get in trouble for it no matter what. I would see a cop letting you go if you are from a very rural area especially if you were driving a truck. It would be easy for a cop to infer that the knife is not to threaten other drivers, but it has a legitimate purpose then. Conversely, in a major metropolitan area there is no reason for one to drive around town with a 7" knife so they might treat it more harshly. Best advice is to keep the knife out of your car as much as possible. In populated areas you will not need a large knife to survive, but if its protection you want then exercise some of your uniquely Texan rights and get a CHL. Then you can legally carry a gun with you, and police cannot charge you with a crime.
See knife can be legal as long as you keep it in private location, such as at your home in the kitchen. If yo do carry a knife, be sure to have a sheath or cover so that it won't do any harm accidentally. Here is how experts define illegal knife as: 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, stilletto, and poniard; (D) bowie knife; (E) sword; or (F) spear. Most of the state laws are ambiguous and the rules and regulations they put up for public are either poorly defined, or not mentioned at all. In large part, critics argue that this vagueness was done intentionally - so that local police and judges can have the final and wide discretion. So before you carry knife with your or in the car, think twice or better yet make sure you know the law to prevent yourself from getting caught and imprisoned.