Your application presents a large number of rows to users, and you need the column headings and summaries to remain fixed in place so that as the user scrolls through table rows the column headings and summaries are always visible.
With WebGrid you can set the DisplayLayout.StationaryMargins property to make the first band’s column headings, column footers (when column footers are visible), or both, permanently fixed in place while users can continue to scroll rows vertically within the framed viewport.