A large sheet of parchment could be folded several times in order to produce several pages for a book. The term quire is used to describe a group of leaves that are all grouped together. In the example below, a single sheet of paper is folded and cut in order to produce a quire with four leaves (eight pages, front and back).
How to make a four-leaf quire:
1. Take an ordinary sheet of paper and fold it twice.
2. The folded piece of paper will need to be sliced twice at the top.
3. The final quire consists of four leaves (eight pages).
A typical parchment quire consisted of eight leaves (sixteen pages), and could be formed by using the above method and adding an extra fold. As you can see, this would require the initial sheet of parchment to be quite large.
Papyrus was not manufactured in sheets as large as parchment, so papyrus codices typically did not use this method of forming quires. A papyrus quire consisted of several sheets folded once, so that each sheet formed two leaves; one sheet then formed the two inner leaves and another sheet formed the two outer leaves (the first and last) of the quire. Some papyrus codices consisted of over 100 leaves in a single quire!
Typically, many small quires were bound together to form the full codex. This is not much different than how modern books are made. Look closely at the spine of a book and you will see that the binding looks wavy. Each little wave is a quire of leaves, which are today usually held together with glue. In ancient times, the quires would be sewn together.