What is "calking iron"

Calking \Calk"ing\, n. The act or process of making seems tight, as in ships, or of furnishing with calks, as a shoe, or copying, as a drawing.

Calking iron, a tool like a chisel, used in calking ships, tightening seams in ironwork, etc.

Their left hand does the calking iron guide.
--Dryden.

n. A tool like a chisel, used in calking ships, tightening seams in ironwork, etc.