This vertical slide is not a Clisby production, but a simple, neat and clever adaptation by Dr. Peter Clark of England.
It utilises a standard cross slide, mounted on bracket which in turn is held by a clamp to a steel plate secured to the lathe cross slide with 4 Allen screws.

A simple (but beautifully made) vice is fastened to the top of the slide - the elements of its construction are obvious from the picture.