Deep-sea Lead Line

This line is 100 fathoms in length, and is marked as follows:

At 10 fathoms with a tucked strand having one knot.

At 20 fathoms with a tucked strand having two knots.

At 30 fathoms with a tucked strand having three knots.

And so on to 100 fathoms. Between these even ten-fathom marks a strip of leather may be used to represent 15 fathoms, 25 fathoms, 35 fathoms, etc.