In double-hung windows, a device usually operated with a spring, designed to counterbalance the window sash without the use of weights, pulleys, and cords.
Illustrated Dictionary of Architecture Copyright © 2012, 2002, 1998 by The McGraw-Hill Companies, Inc. All rights reserved
A spring-loaded device, usually a spring balance or tape balance; used to counterbalance a sash in a double-hung window; eliminates the need for sash weights, sash cords, and pulleys.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.