bonding stone

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bondstone, bonder

In stone masonry, a stone usually set with its longest dimension perpendicular to the wall face so as to tie the masonry wall to its wall backing. A very large bondstone may be set with its long dimension parallel to the wall face and still serve as a bonder, provided that its width is sufficiently large to tie it to the wall backing.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.