Why do ninjas usually replace their own body with a block of wood?


Take as an example the Body Replacement Technique from the Naruto series.

Using this technique, any user can replace his own body with some other
object, but most of the time ninjas replace their body with a block of wood.
This has also been seen in the Naruto series when Kakashi takes the exam of
Naruto's team.

So the thing which really bothers me is that they replace themselves with a
block of wood, and not something else. I have even seen this type of event
happen in other anime. It is quite common for ninjas to replace themselves
with a block of wood.

[![block of wood at a location presumably occupied by a ninja just moments
before](https://i.stack.imgur.com/kEe8Q.jpg)](https://i.stack.imgur.com/kEe8Q.jpg)




In-universe, no reason is given apart from the fact that every time I can
recall this happening they were near trees and thus a chunk of wood was
convenient. The actual source is never addressed, and we never see trees
falling over because they lost a chunk of themselves.

For the real-world reason...It's a Japanese trope based on the actual legends
built up around historical Ninjas (probably also _by_ said Ninjas, for whom
misinformation was a great tactic). "Kawarimi" was a supposed technique
possessed by the ancient Ninja that used misdirection and split-second timing
to swap places with something that could easily be mistaken for the Ninja.

There may be some historical grounds for this, but not to the extent we see in
Naruto. Instead, this could easily be a trick used by historical ninja to
trick and mislead enemies, and build up the mythos they had constructed for
themselves. As an example, a Ninja may have previously prepared a wooden dummy
that was about his size and dressed it in the same clothing as he was wearing.
This dummy could be hidden somewhere convenient for later use. Then, when
fleeing pursuers, you head back to where you hid the dummy and in a moment
where your pursuers lose track of you (either with natural obstacles or a
smoke/flash explosive set off), you set the dummy in your place and go the
other direction. You could even set it up to go over a cliff. While your
pursuers are distracted by the dummy, you slip away. Thus was built up the
legend that Ninjas could 'trade places' with things, and since wooden (or
straw) dummies were convenient for those purposes, they likely got used the
most.

Over time, this morphed in Japanese culture along with a lot of the other
myths of the Ninja. For example, the myth of Ninja dressing in all black
growing out of Kabuki Theater (Stage hands dressed in all black, and so
theater goers were used to completely ignoring them...so when one of them
jumped out and drew a sword, it was as if they had appeared from
nowhere...allowing the theater to have 'super-stealthy Ninjas'). Over this
time, the idea of the Kawarimi morphed and changed until it landed on them
simply swapping places with a log. Even the particular appearance of the log
is somewhat standardized in this trope: a short round chunk of wood of about
the same thickness, either completely smooth or with a single 'stump' branch
coming off the side.

It turns up in quite a number of places, from other anime and manga to a bunch
of video games. In short, in Japanese culture, the "kawarimi log" is simply
the standard thing for a Ninja to swap places with, without regard for where
it came from. It's the same idea as how, in American culture, if something is
blindly tossed out a window, there _will_ be a cat down there that yowls and
knocks over a bunch of stuff over...or how no one questions that saying "Well,
at least it can't get any worse" will instantly make things worse...or how
someone can put on a pair of glasses, and that is considered a solid disguise.

So, while there is no in-universe explanation...the out of universe
explanation is simply "it's a standard narrative tool in Japanese culture."




In-universe, no reason is given apart from the fact that every time I can
recall this happening they were near trees and thus a chunk of wood was
convenient. The actual source is never addressed, and we never see trees
falling over because they lost a chunk of themselves.

For the real-world reason...It's a Japanese trope based on the actual legends
built up around historical Ninjas (probably also _by_ said Ninjas, for whom
misinformation was a great tactic). "Kawarimi" was a supposed technique
possessed by the ancient Ninja that used misdirection and split-second timing
to swap places with something that could easily be mistaken for the Ninja.

There may be some historical grounds for this, but not to the extent we see in
Naruto. Instead, this could easily be a trick used by historical ninja to
trick and mislead enemies, and build up the mythos they had constructed for
themselves. As an example, a Ninja may have previously prepared a wooden dummy
that was about his size and dressed it in the same clothing as he was wearing.
This dummy could be hidden somewhere convenient for later use. Then, when
fleeing pursuers, you head back to where you hid the dummy and in a moment
where your pursuers lose track of you (either with natural obstacles or a
smoke/flash explosive set off), you set the dummy in your place and go the
other direction. You could even set it up to go over a cliff. While your
pursuers are distracted by the dummy, you slip away. Thus was built up the
legend that Ninjas could 'trade places' with things, and since wooden (or
straw) dummies were convenient for those purposes, they likely got used the
most.

Over time, this morphed in Japanese culture along with a lot of the other
myths of the Ninja. For example, the myth of Ninja dressing in all black
growing out of Kabuki Theater (Stage hands dressed in all black, and so
theater goers were used to completely ignoring them...so when one of them
jumped out and drew a sword, it was as if they had appeared from
nowhere...allowing the theater to have 'super-stealthy Ninjas'). Over this
time, the idea of the Kawarimi morphed and changed until it landed on them
simply swapping places with a log. Even the particular appearance of the log
is somewhat standardized in this trope: a short round chunk of wood of about
the same thickness, either completely smooth or with a single 'stump' branch
coming off the side.

It turns up in quite a number of places, from other anime and manga to a bunch
of video games. In short, in Japanese culture, the "kawarimi log" is simply
the standard thing for a Ninja to swap places with, without regard for where
it came from. It's the same idea as how, in American culture, if something is
blindly tossed out a window, there _will_ be a cat down there that yowls and
knocks over a bunch of stuff over...or how no one questions that saying "Well,
at least it can't get any worse" will instantly make things worse...or how
someone can put on a pair of glasses, and that is considered a solid disguise.

So, while there is no in-universe explanation...the out of universe
explanation is simply "it's a standard narrative tool in Japanese culture."

