expression
too lazy to do anything; won't lift a finger
Idiomatic expression describing extreme laziness: someone who won't even turn a horizontal object vertical, i.e., won't do the simplest task. Often used in negative form (～しない). Compare with 縦の物を横にもしない, which has the same meaning.
See also: 縦の物を横にもしない
彼は本当に横の物を縦にもしない怠け者だ。
He's such a lazy person that he won't even lift a finger.
休日は横の物を縦にもしないで、ずっと寝ていた。
On my day off, I didn't do a single thing and just slept all day.
A set phrase literally meaning 'not even turning a horizontal thing vertical', implying an unwillingness to perform the simplest action. The exact origin is uncertain, but it vividly illustrates extreme laziness.