sand-rammer

from The Century Dictionary.

• noun A wooden tool, used by hand in the making of sand-molds in a foundry, by which the sand is compacted in the flask around the pattern. Large ones are used with two hands and smaller ones with one.
• noun A mechanical apparatus used for the same purpose, operated by compressed air, particularly in connection with power molding-machines.
• noun A combination of power-rammers used to produce a uniform pressure all over a flask by pneumatic pressure brought upon all at once, with equalizing lovers to prevent concentration of pressure at any point.