plumb line
Longman Dictionary of Contemporary English 5++LDOCE 5++ˈplumb line noun [countable] TZa piece of string with a small heavy object tied to one end, used for measuring the depth of water, or for checking whether something such as a wall is built exactly upright 铅垂线，垂直线
Examples from the Corpus
plumb line• If any walls appear to lean, check by going back to the nearest upper window and drop a plumb line down.• But again, as with the lintels, the union did not allow the bricklayers to use a plumb line.ˈplumb line nounChineseSyllable
Corpus object of a heavy small with tied a string piece
plumb line
ˈplumb line
noun [countable]
a piece of string with a small heavy object tied to one end, used for measuring the depth of water, or for checking whether something such as a wall is built exactly upright
ˈplumb line
noun [countable]a piece of string with a small heavy object tied to one end, used for measuring the depth of water, or for checking whether something such as a wall is built exactly upright