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

# Edit build requirements

> Add, remove, and configure build requirements on an aBOM, including quantities, substitutes, reference designators, and Made on Assembly parts.

The Part Installs (aBOM) dialog lets you edit an aBOM's [build requirements](/build-hardware/bills-of-materials) directly: add a part to the build, delete one, set the quantity, configure substitutes, and call out Made on Assembly (MOA) parts.

## Prerequisites

* Permission to edit aBOMs on the part inventory you're working with.
* An existing aBOM. ION creates one automatically when a part inventory is staged for a build.
* The **Part Installs (aBOM)** dialog is open. You can launch it from a part inventory page or from inside an active run.

## Open Part Installs (aBOM)

The dialog shows the parent assembly card at the top, then a searchable list of build requirements for that assembly. If you're working inside a sub-assembly, breadcrumbs at the top of the dialog let you navigate back up the assembly tree.

## Turn on Edit Mode

Toggle the **Edit Mode** switch in the bar at the top of the dialog. In edit mode you see a **You are in edit mode.** banner with a **Learn More** link, and the add-part dropdown becomes available. Add, delete, and quantity changes are available only while edit mode is on.

## Add a part

1. With edit mode on, open the **part dropdown** under the edit-mode banner.
2. Select the part to add. ION creates a new build requirement with a quantity of 1.
3. Optional: Turn on the **Add as MOA** switch before selecting to mark the part Made on Assembly. See [Made on assembly (MOA)](/build-hardware/bills-of-materials/made-on-assembly).

The dropdown excludes parts that are already on the aBOM, so you can't add the same part twice.

## Set the quantity

In edit mode, each build requirement card has a **quantity** input representing the count of that part required to complete one parent assembly. ION multiplies this by the parent assembly's quantity to compute total demand for the build. When the run builds more than one parent unit, the input is labeled **/ assembly** to make the per-assembly unit clear.

<Note>
  Quantity is per one parent unit. If the parent has a quantity of 5, ION calculates total demand as `quantity × 5`.
</Note>

## Configure substitutes

Expand a build requirement card and open the **Substitutes** dropdown to add alternate parts that can be installed in place of the primary part. When operators install against this build requirement during a run, they can scan any of the listed substitutes to satisfy the requirement. For more information, see [Alternates and substitutes](/build-hardware/bills-of-materials/substitutes).

## Add reference designators

For build requirements that need positional callouts, such as `R12` or `U7` on a PCB, expand the card and open the **Reference Designators** dropdown to enter them. Each designator must be unique within the build requirement and counts toward the total quantity required. For more information, see [Reference designators](/build-hardware/bills-of-materials/reference-designators).

## Delete a build requirement

In edit mode, click the trash icon on a build requirement card. ION shows a **Delete Build Requirement** confirmation; click **Delete** to confirm. Any build requirement can be deleted, whether it came from the mBOM or was added by hand.

<Warning>
  You can't delete a build requirement that already has installed inventory. Remove the recorded installations first, then delete the requirement.
</Warning>

<Tip>
  The **Show only incomplete** switch at the top of the dialog hides build requirements that already have full installations recorded, which helps when working through a long aBOM late in a build.
</Tip>

<Tip>
  The **Expand All** / **Collapse All** button toggles every build requirement card open or closed in one click, so you can review substitutes, MOA settings, and installations across the whole aBOM at once.
</Tip>

<Tip>
  Click **Expand ABOM** on a build requirement whose part is itself an assembly to drill into that sub-assembly's aBOM. The breadcrumbs at the top of the dialog let you walk back up the assembly tree at any point.
</Tip>

<Tip>
  Use the **Search** box to narrow the build requirement list by part number or description while editing.
</Tip>

## Related

* [Bills of materials](/build-hardware/bills-of-materials)
* [Parts](/build-hardware/parts)
* [Runs and execution](/build-hardware/runs-and-execution)