picture a mantel scarf. hanging over both sides of the bed, at the foot. decorator-style to match the drapes or carpet or what-all. it might have fringe on the edge or crochet or tassels or nothing. it might be fancy or simple depending on the style, just like a mantel scarf. it serves no other purpose than to be decorative. it might lie across a bedspread as another layer, or across a blanket looking like a folded bedspread.
http://www.designerliving.com/Bed-Runners-C93.aspx
http://www.plowhearth.com/product.asp?pcode=10847
http://www.globalsources.com/manufac...ed-Runner.html
that should give you an idea of what they look like.