For example, folios were rarely made by simply binding up a group of two leaf gatherings; instead several printed leaf pairs would be inserted within another, to produce a larger gathering of multiple leaves that would be more convenient for binding.[5]: 30–31 For example, three two-leaf printed sheets might be inserted in a fourth, producing gatherings of eight leaves or sixteen pages each. Bibliographers still refer to such books as folios (and not octavos) because the original full sheets were folded once to produce two leaves, and describe such gatherings as folios in 8s. Similarly, a book printed as an octavo, but bound with gatherings of four leaves each, is called an octavo in 4s.[5]: 28