noun
access hole; inspection opening
A small door or hatch, often in a floor, ceiling, or wall, for maintenance access. Common in building and equipment contexts.
天井の点検口から配管を確認した。
I checked the pipes through the ceiling access hole.
床下の点検口を開けて、湿気がないか調べた。
I opened the underfloor inspection hatch and checked for dampness.
Compound of 点検 (inspection) and 口 (opening). The spelling 孔 (hole) is a less common variant.