legal blade lengths vary state to state, and even city to city. usually anything under 4 inches actual blade is cool, if you don't have it concealed. I used to carry a legal legth knife in my boot, but stopped. I got punched in the stomach wicked hard by a state trooper who saw it.
now I carry a 3 1/2 length (blade) folding knife clipped to the chest strap of the pack. real visible. and a can of wasp and hornet spray on my right hip, next to my water. just as effective as mace, but will spray a 15 or so foot stream. great for getting scumbags to back off. just spray it off to the side, and then point it at their face. trust me, they stop.
plus it's legal to carry. if the cops hassle you, tell them you are severely allergic to bees and wasps and could die if stung... yadda yadda, do you finest "scared" BS and you're gravy.
plus I'm a big guy, with a hardwood walking stick. Most people actually move away from me, specially in the dark. but I'm just a teddy bear... Honest:evil: