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With the aid of a bow drill and sand, the pipe has cut a circular hole into the stone. But how can the drillers get the central core out? Stocks wedges two chisels into the circular groove. The core breaks off at its base. Stocks reaches in and plucks it out, leaving a hole behind not unlike the ones once cut by the Egyptians. Previous How Big Were They? | Cutting Granite with Sand | NOVA Raises an Obelisk Lever an Obelisk | Explore Ancient Egypt | Mysteries of the Nile | Resources | Transcript Medieval Siege | Pharaoh's Obelisk | Easter Island | Roman Bath | China Bridge | Site Map Editor's Picks | Previous Sites | Join Us/E-mail | TV/Web Schedule About NOVA | Teachers | Site Map | Shop | Jobs | Search | To print PBS Online | NOVA Online | WGBH © | Updated November 2000 |