針の穴から天を覗く
(Hari no ana kara ten wo nozoku;
“To peer at the heavens through the eye of a needle”)

Definition:

Attempting to solve big, complicated problems or deal with issues requiring expertise, despite only having a small supply of knowledge. Trying to grasp something vast even though one’s point of view is extremely limited, like trying to see the entire span of the sky through the eye of a needle. It generally applies when someone tries to share their thoughts or take charge despite being out of their depth.

Breakdown:

We begin with the noun 針 (hari), “needle,” followed by the associative particle の (no) in its possessive function. The thing possessed by the needle is the noun 穴 (ana), “hole.” This entire noun phrase is marked by the particle から (kara) as the source “from” which one performs the sentence-final verb 覗く (nozoku), “to peek at,” “to examine,” etc. This verb appears in conclusive form. And immediately preceding it, we find the object-marker particle を (wo) marking the noun 天 (ten), “the sky,” “the heavens.”

Notes:

This phrase is considered to be synonymous with 葦の髄から天井を覗く; only the particulars and nuance are changed. There are quite a few other variations on the same theme, including 管を以て天を窺う (kuda wo motte ten wo ukagau, “to examine the heavens through a tube”) and 貝殻で海を量る (kaigara de umi wo hakaru), “to measure the ocean with a seashell.”

This is the は entry of the Kyoto iroha karuta set.

(Trivia of the day: While writing the example sentence, I learned that certain proper nouns – including OS names – are commonly written with the alphabet instead of being transliterated into Japanese. The phonetic rendition of “Linux” is リナックス (rinakkusu), but simply inserting “Linux” into Japanese text as-is is considered correct, and easier to parse than sounding out and deciphering the katakana would be.)

Example sentence:

「パソコンの初心者でもLinuxを使うことはできるけど、だからと言ってLinuxをインストールして、設定変更も簡単だと思ったら針の穴から天を覗くようなものだ」

(“Pasokon no shoshinsha de mo Linux wo tsukau koto wa dekiru kedo, dakara to itte Linux wo insutoooru shite, settei henkou mo kantan da to omottara hari no ana kara ten wo nozoku you na mono da.”)

[“While even first-time PC users may be able to use Linux, thinking that therefore it would be easy to install it and adjust its settings reveals a deep lack of knowledge compared to the scope of the task.”]