I have wanted a horizontal vise for my Makita 1013 slider for some time. $60-$80 +shp. I also wanted to try making a quick release from a hex nut.
This thing is built from my scrap pile and whatever I had lying around except for the 5/8 all-thread, nut and spring which I got at HD.
Not pretty but it works well.
.PDF of drawing is attached in addition to the .jpg.
Enjoy.