畑はたけ水すい練れん

noun

useless book learning; armchair theory

Idiomatic and jocular expression for knowing theory but being unable to apply it, likened to practicing swimming in a field. The literal meaning is 'field swimming practice'.

• いくらマニュアルを読よんでも畑はたけ水すい練れんだよ。実じっ際さいにやってみないと。

  No matter how much you read the manual, it's just useless book learning. You have to actually try it.

• 彼かれの知ち識しきは畑はたけ水すい練れんで、現げん場ばでは役やくに立たたない。

  His knowledge is all theory and no practice; it's useless in the field.