calking

CIDE DICTIONARY

calking, 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.  [1913 Webster]
"Their left hand does the calking iron guide."  [1913 Webster]

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