| 摘要 |
An instrument for ascertaining whether a surface is horizontal, vertical, or at a 45* angle, consisting essentially of an encased, liquid-filled tube containing an air bubble that moves to a center window when the instrument is set on an even plane. Also called a spirit level. A box level including an elongate body, plumb and level vials, and spaced handholds having outer edges together defining first and second parallel application planes beyond first and second face planes of the elongate body.
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