 This would have the advantage that vertical dot combinations could be printed in a single impact, without requiring fine rotation control of the platen roller.However it would require a specialised daisy wheel so printing of a letter and letterhead would require a two-step process with a manual wheel change in-between.As the development of this technique post-dated the widespread availability of 24-pin dot matrix printers and coincided with the arrival of affordable laser printers in offices, it was never a popular approach.