This is a spline jig that I made using the "Blackies" jig as a model. The scrap wood I used happened to be cut at a 45 degree angle so it looks kind of cool but has nothing to do with the function.
Looks like it does the job.
I would make sure those bottom sections in contact with the table do not hang up in the miter grooves. I noticed in the pict that one of yours is very close to possibly dropping in to the groove. A solid board all the way across the bottom would be a safety feature.
Thanks for the feedback, but it rides on the fence and moves with the fence sideways. This was set up for the picture, I would normally center it on the table and move the adjustable end pieces to were I want the groves.