A4 folded full colour leaflets

Imagine the world before some clever Henry invented folding. Imagine the size of the linen cupboard you'd need to fit your duvet cover in? Well, if you've got more to say than you can fit on a leaflet, get a bigger leaflet and fold it. Makes sense really. They're easier to handle, cheaper than a booklet and cheaper to mail out (if you follow Royal Mail's guidelines).