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Sounding Leads: Weights & Leadlines


A sounding lead can be used as a primary depth-finding device, or as a backup for electronics. It is typically attached to a light line which is measured off with bands, tags, knots, or paint markings every fathom or so (known as a 'leadline').


Sounding leads can be used for position-finding and dead reckoning on coastal passages, or when making landfall from an offshore position. When used in conjunction with GPS and a depth sounder, the peace of mind that comes from being able to verify the accuracy of electronic readings cannot be overstated.

For cruising, sounding leads also offer the advantage of being portable so the exact depth can be checked ahead of time... perhaps from a dinghy. This can be incredibly useful for surveying small creeks, narrow channels, inlets, anchorages, marina slips, and other areas where the exact depth might be uncertain. 


Sounding leads are traditionally manufactured by pouring hot lead into a casting mold. The process itself is low-tech, and no two leads are exactly alike. However some designs are better than others, and we've had these custom made to ensure that each of our sounding leads incorporates the very best and most useful features -

  • Octagonal shaped cross-section prevents spinning while deployed. Flat sides can't roll around when placed on deck, or stowed below in a locker. 
  • Recessed bottom with grooves can be packed with tallow or grease for picking up bottom samples (sand, mud, pebbles, grass, etc.)
  • Large, built-in cast eye for attaching leadline rope up to 3/8" diameter
  • 3lb weight is suitable for inshore soundings at slow speed, dinghy, etc.
  • 7lb weight is recommended for offshore/coastal soundings and navigation

  • 100% pure lead - Made in USA


We have attached a sketch (above) which shows how to attach the sounding lead to the leadline. Basically you're just passing the long spliced eye through the cast hole, then looping it back onto itself. This is the favored traditional method because it eliminates the need for any additional hardware (shackles, etc), and also  helps prevent spinning if the vessel is traveling through the water or making way. 
Marking /Tagging the Leadline
Government and military vessels, including US Navy and Coast Guard, will generally use the leadline marking system as prescribed in US gov publication NSTM 581 2-6:

For non-government vessels however, there are lots of ways to mark a leadline, mostly depending on personal preference and how/where it will be used. It can be measured off and tagged in feet, fathoms or meters. The marks themselves are usually made with leather or canvas strips, knots or seizings (sometimes paint markings) at the desired intervals. 
For a traditional example, a narrow strip of rawhide or canvas might be inserted to the rope (tucked into the strands)  at 6-foot intervals (1 fathom) with notches to differentiate between 1 fathom, 2 fathoms, 3... etc... plus maybe marks at 1-foot intervals for the first 6 feet or so (for better precision in very shallow water). The old timers prefer this type of 'tagging' because it can be "felt" at night... no flashlight or lantern necessary. 
However in more contemporary times... where the sounding lead will probably be used as a supplement to electronics... the accepted practice is to apply unique paint marks, (or color coded sail twine whipping)  at the desired intervals... 1 band = 1 fathom, 2 bands = 2 fathoms, and so on.