: A friend convinced me to try sandpaper mounted on a piece of plate glass as a
: method of sharpening my hand tools. What grits are recommended? Where can
: I purchase this material? Any guidance appreciated!

The finish crew I worked on used wet-dry sandpaper flat on the bed of the table saw to hone plane soles flat, and also to do the final honing on plane irons and chisels, particularly offset (rabbet) chisels. I don't remember the grit, probably just whatever we had laying around. The water on the wet-dry effectively stuck the paper to the table saw top. It worked very well - very sharp, if not scary-sharp.