T-Slot allows for adjusting clamp for angle cuts. Not alternate location for 6-1/4'' lag bolt allows for larger parts. Bolt can also re-located closer end of jaws.
From Woodsmith Tips. Handy jig for holding small parts. Modified to include T-Slot for attaching to miter-gauge. Opposite end of Jaws adjusted to width of the small part.
http://woodworkingtips.com/etips/2009/02/12/sn/print