sand jack


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sand jack

A box having tight joints which is filled with dry, clean sand on which rests a tight-fitting plunger; the plunger supports the bottom of posts used in centering; when it is desired to lower the centering, a plug in the bottom of the box is removed, allowing the sand to run out.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.
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