gagger

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun One that gags, as a piece of metal used to keep the core in position in a foundry mold.

from The Century Dictionary.

• noun One who gags.
• noun In molding: A tool used to lift the sand from a flask.
• noun An iron so shaped that when placed in a mold it keeps the sand from breaking apart.
• noun An iron used to hold in position the core of a mold. Also called chapelet and grain.

from the GNU version of the Collaborative International Dictionary of English.

• noun One who gags.
• noun (Founding) A piece of iron imbedded in the sand of a mold to keep the sand in place.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A piece of iron embedded in the sand of a mold to keep the sand in place.