Window Trough : That part of the window sill below both the upper and lower vertical sliding sashes of sash windows, or the area of the sill or frame covered by a closed casement or top hung window
Ministry of Business, Innovation and Employment, Glossary of terms and acronyms, Wellington, New Zealand 2010. http://wwwsosh.govt.nz/resources/glossary-u.shtml, (Occupn Hlth and Sfty - Brit) {530}