Some manufacturers were more proficent in particular techniques, styles and colours than others. Also different clays were used and some processes were exclusive to one or two factories. The rail back is the easiest back to make. The bar back is essentially no different to the rail back in manufacture though it may be more likely made on a milling machine rather being ground. On a bar back the raised 'bars' are about equal width to the hollows.
Rails are about half the width or smaller.
The portculis back is a rail back ground in both directions. Ring backs are the least common of the four main types but nevertheless there are many variations. They would all need to be made on a lathe. They seem to be more often found on majolica tiles, perhaps as the engineering company who made the pattern dies could easily produce the back dies too. Just the rail back is shown but the same applies for bar and portculis backs too.