Such implements could certainly be considered dangerous weapons, since all are capable of inflicting serious, even fatal injuries: as a historical note, for example, Japans' most famous (and arguably greatest) swordsman, Miyomato Musashi, killed another great swordsman with a wooden oar, and fought a number of bouts with wooden swords. The law does not specifically define what is a weapon, since essentially any implement which magnifies the effect or damage of an attack or blow is a weapon; the number of weaons is therefore essentially infinite. Since clubs are certainly weapons and what you describe are essentially clubs, they would almost certainly be considered weapons, too.In terms of self-defense: the general rule is proportionality of response. If someone pushes you or punches you once in the face and you crack his skull with a bokken, you have responded disproporationiately and could easily be convicted of assault and battery--you used excessive force under the circumstances. On the the hand, if assault was continuing and/or the attacker was much larger or stronger than you, so that injury even a bar handed attack is reasonably likely or foreseeable, using a club, jo stick, bo stick, baton, shinzai, bokken, etc. is reasonable. And, of course, it is reasonable to use a weapon against another weapon, or to even the odds when outnumbered. It is not about a hard-and-fast rule of what implements may be used in self defense or not: it's about matching the defense to the threat.