you are correct about there being no length law in California. however, a knife in your pocket can be considered concealed. Once they added the lipstick knife and the writing pen knife to penal code 12020 they opened the door for an officer, with his own interpretation to think that a credit card knife may be illegal. You never stated what state you were in. so Check your local laws.

Think of it this way... if you have a switchblade in your pocket it is illegal... the moment a police officer finds it in your pocket. Noone needs to know you have it. If you have your credit card knife... it would take someone KNOWING you had it in your possession.

(a) Any person in this state who does any of the following
is punishable by imprisonment in a county jail not exceeding one year
or in the state prison:
(1) Manufactures or causes to be manufactured, imports into the
state, keeps for sale, or offers or exposes for sale, or who gives,
lends, or possesses any cane gun or wallet gun, any undetectable
firearm, any firearm which is not immediately recognizable as a
firearm, any camouflaging firearm container, any ammunition which
contains or consists of any flechette dart, any bullet containing or
carrying an explosive agent, any ballistic knife, any multiburst
trigger activator, any nunchaku, any short-barreled shotgun, any
short-barreled rifle, any metal knuckles, any belt buckle knife, any
leaded cane, any zip gun, any shuriken, any unconventional pistol,
any lipstick case knife, any cane sword, any shobi-zue, any air gauge
knife, any writing pen knife, any metal military practice
handgrenade or metal replica handgrenade, or any instrument or weapon
of the kind commonly known as a blackjack, slungshot, billy,
sandclub, sap, or sandbag.


For the rest see here californiaccw.org/files/pen...12040.html