Small knives permitted in carry-on luggage must meet all of the following requirements:
|The blade must be no more than 2.36 inches or 6 cm in length – from tip to where it meets the handle or hilt|
|The blade must be no more than ½ inch in width|
|Knives with locking or fixed blades|
|Knives with molded grips|
|Razors and box cutters|
As you can see, any knives carried on must be of the folding variety. I have never used a folding knife before, but I know they're fairly common.
One thing that hasn't changed is this last word from the TSA: "The final decision rests with TSA on whether to allow any items through security checkpoints." So....don't take your favorite knife!