This jig marries an inexpensive Bessy portable bench vise to the LittleRat.  The primary purpose of the jig is to hold parts closer to the baseplate (and cutter) than the normal clamp allows.  The WoodRat miter box accessory provides this same function and more however this jig is a little easier to set up and operate.

The router baseplate has been removed for clarity.

The jig attaches to the LittleRat via four threaded 8mm x 1.25 bolt holes that already exist in the carriage.   The attachment plate is a piece of 1/2" MDO plywood that has been profiled on the back to stand proud of the extrusion just a little. 

The fixed section of the vise is screwed to the platform.  It is held away from the face or the extrusion to allow for an area of through cutting if required. 

The platform is attached to its plate using four 1/4-20 bolts.  This was used instead of glue because it would allow the platform to be biased to counter any effect of tipping the carriage due to the cantilever weight this jig could impose.  It turns out there was no need to bias the platform but it's a good idea to allow for it anyway.

The attachment plate appears a little over-long on the back side, this was done to provide a place to mount some form of cursor at a later date.