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1. Any horizontal beam, joist, or member which supports a load.
2. A support for a landing or winder in a stair.
3. The ribbon board in balloon framing, which supports second-floor joists.
4. A horizontal member of a scaffold upon which the platform rests and which may be supported by ledgers.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.