From how I interpret the RCW, any fixed blade knife is illegal to conceal, but can be carried openly. Any length folder is legal to conceal. Kind of dumb, but those scary/evil looking black rifles... er.. uh... fixed blade knives can't be trusted.
Too confusing for this dumb old fart, if I am going to a place I have not been or seems to be a grey area for what I carry I contact them. Talk to head LEO that area get name when talked to tell them you will keep info with there name on your person and that's worked well for me.
About 15 years ago in Seattle I had to defend myself against four guys who jumped me on Lower Queen Anne. I was carrying a 3.75" knife, used it to dissuade further assault without shedding blood, then called the police because they were idiots and needed to get arrested. SPD looked at the knife, measured it, said they were keeping it and to call the evidence room the next day. I also got to take a cruiser ride down to where they pulled said idiots over and got to ID them before they went down to the Graybar Hotel for a free night's hospitality.
I never called the evidence room, not getting stomped was well worth the $27.99 I paid for it, and I never heard anything from SPD.
Posted from my car phone.
I live near Seattle, with it's 3.5" folding blade limit, but I'm often in cities where 3" is the limit. So my carry knives are 3" or less. A Benchmade Mini Griptilian, or an Emerson CQC-14.
Be very careful with blades in Washington. If you are caught with a "dangerous weapon" it can result in loss of your concealed carry rights. Look in the RCW it is mentioned
Weapons apparently capable of producing bodily harm — Unlawful carrying or handling — Penalty — Exceptions.
(1) It shall be unlawful for any person to carry, exhibit, display, or draw any firearm, dagger, sword, knife or other cutting or stabbing instrument, club, or any other weapon apparently capable of producing bodily harm, in a manner, under circumstances, and at a time and place that either manifests an intent to intimidate another or that warrants alarm for the safety of other persons.
(2) Any person violating the provisions of subsection (1) above shall be guilty of a gross misdemeanor. If any person is convicted of a violation of subsection (1) of this section, the person shall lose his or her concealed pistol license, if any. The court shall send notice of the revocation to the department of licensing, and the city, town, or county which issued the license.
"It is foolish and wrong to mourn the men who died. Rather we should thank God that such men lived." -G.S. Patton