noun
A tool used to check whether a surface is horizontal or vertical. Often used in construction and DIY. Synonymous with 水準器 (すいじゅんき).
See also: 水準器 (すいじゅんき)
棚を取り付ける前に、水平器で傾きを確認した。
Before installing the shelf, I checked the tilt with a spirit level.