b.striding level: a spirit-level supported at both ends so as to straddle over intervening projections. So striding stand.
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society > occupation and work > equipment > equipment for marking out work > [noun] > level
level1340
water level1563
leveller1693
spirit level1718
pendulum level1728
bubble level1814
Y level1845
striding level1878
1878 J. N. LockyerStargazing 332 Place a striding level on the pivots.
1890 W. F. StanleySurveying Instruments 222 In the construction of the striding level,..the two striding stands SS are carried down from the ends of the casing tube B of the spirit level.