くぐり戸(ど)

くぐりど
noun
low doorway; small wicket door
buildingculture
1. low doorway; small wicket door; crawl-through door
A small, low door set within or beside a larger gate or wall, low enough that a person must stoop or duck to pass through. Common in traditional Japanese architecture, tea houses, and temple gates.
I entered through the low doorway.
茶室(ちゃしつ)にはくぐり戸(ど)がついている。
The tea room has a small wicket door.
I lowered my head and quietly slipped through the low doorway.

From 潜(くぐ)る (to duck under, to pass through) + 戸(と) (door). The verb element captures the stooping motion required to enter.

Common collocations

Cultural note

In tea ceremony, the low entrance (躙口(にじりぐち)) is a famous example: guests must crouch to enter, symbolizing humility and equality regardless of rank.