> ## Documentation Index
> Fetch the complete documentation index at: https://docs.gtfo.vc/llms.txt
> Use this file to discover all available pages before exploring further.

# Books & units

> Order book structure and unit-based sizing.

## Books

* Two books per pair: **base→quote** (sell base) and **quote→base** (sell quote). We refer to them by a deterministic `BookId`.
* Each book is defined by a **BookKey**: `(base, quote, unitSize, makerPolicy, takerPolicy)`.
* Orders in a book share the same `unitSize` and fee policies. Units are **integers**; the notional is `unit * unitSize` in the *book's base currency*.

## Units

Every book has a fixed `unitSize` (an amount of **base** for that book). All maker sizes are expressed in **units** (uint64). Actual base/quote amounts are derived from the `unitSize` and the tick's price.