# Serials

> Serial statuses, the timeline, as-built versus as-maintained.

A serial is one physical unit: one `COMPONENT` or `ASSEMBLY` that you track by number. Every serial has a status, a location and a history. Open one from **Inventory**, on the **Serials** tab, or from the **Units** tab of a build order. The operations are `listSerials` and `getSerial`.

## Statuses

| Status | What it means |
|---|---|
| `WIP` | The unit is being built and is not finished yet. |
| `AVAILABLE` | The unit is in stock and free to use. |
| `RESERVED` | A build order has set it aside. |
| `CONSUMED` | It was built into another unit and left stock. |
| `SHIPPED` | It left for a customer. Deploying a device ships its unit. |
| `QUARANTINED` | It is held back, with a reason. It is not available. |
| `SCRAPPED` | It was written off. |
| `RMA` | It came back for repair and is in the return pipeline. |

A unit that passes its final test, or has none, becomes `AVAILABLE` when it is produced. A unit that fails is quarantined. See [Build orders and work instructions](https://dev.buildtrace.eu/docs/concepts/build-orders-and-work-instructions.md).

From a serial's page you can **Move** it to another location, **Quarantine** it, release it from quarantine, or **Scrap** it. The operations are `moveSerial`, `quarantineSerial`, `releaseSerial` and `scrapSerial`. A `CONSUMED`, `SHIPPED` or `SCRAPPED` unit can't be moved, quarantined or scrapped.

## The timeline

The **Timeline** on a serial's page is one event log. Every change to the unit adds an event, and nothing is rewritten. Events include received, moved, reserved, produced, inspection passed or failed, quarantined, released, scrapped, shipped and deployed. Rework adds events too, such as a component replaced or an ECO retrofitted. So does firmware, with `FIRMWARE_FLASHED` and the assignment of a version.

The event log is what you read to answer "what happened to this unit". The operation is `getSerialTimeline`.

## As-built and as-maintained

A unit has two views of what it contains.

The `as-built` record is frozen at production. It lists the components and lots that went in, the work instructions the unit was built to, the test plan and its results, and the ECOs that were applied or skipped. It never changes after that. It appears as **As-Built Genealogy** on the serial's page. The operation is `getAsBuilt`.

The `as-maintained` view is what the unit contains now. Rework changes it. When a technician swaps a component, the old serial detaches and the new one attaches, and the timeline records the change. The as-built record stays as it was, so you can always compare the two.

Service and rework orders live in **Service**. The operations include `createReworkOrder` and `addReworkAction`. The unit's SBOM uses the as-maintained components, so it shows the current parts, not the original ones. See [SBOM export](https://dev.buildtrace.eu/docs/guides/sbom-export.md).

## Using serials in a recall

Because every unit records its lots and components, you can start from a lot, a supplier or a component revision and find every unit that contains it. See [Scope a recall](https://dev.buildtrace.eu/docs/guides/scope-a-recall.md).