o'-ker, (Isa 44:13, "He marketh it out with a pencil," margin "red ochre," the King James Version "line"; seredh, a word found only here, and of unknown etymology): Designates the implement used by the carpenter to mark the wood after measuring and before cutting. "Red ochre" supposes this to have been a crayon (as does "pencil"), but a scratch-awl is quite as likely. Ochre is clay colored by an iron compound.
The International Standard Bible Encyclopedia
Ochre, Red
The International Standard Bible Encyclopedia, James Orr (1915). Public domain, from the CrossWire SWORD module.