Lead Line
F5. The Reference Layer: Glossary, Units, Signals and Information SourcesDefinition
Traditional weighted line for taking soundings.
A lead line is a marked line with a lead weight for measuring depth by hand where an echo sounder is unavailable or unreliable, such as in shoal water alongside or in a boat. The hand lead is marked at set fathoms with leather, calico, and bunting so the leadsman reads depth by feel at night (‘by the mark twain’ is two fathoms). The lead’s hollow base is armed with tallow to bring up a sample of the bottom, confirming holding ground for anchoring.