---
description: >-
  Instructions for managing pre-routed traces in Quilter, including reasons to
  pre-route, handling during layout, and specifying locked routing paths.
---

# Pre-routed traces

### Overview

Quilter considers all traces and vias within the board boundary at the time of file upload to be "pre-placed".&#x20;

**As a foundational rule, Quilter does not alter the path or position of pre-placed traces and vias.** Quilter will not automatically delete unconnected or orphaned trace segments, so be sure to remove them from your input file before submission.&#x20;

During compilation, Quilter will strive to place and route all components that are not already routed. If a pre-routed trace segment is incomplete, Quilter will attempt to finish it during routing.

{% hint style="warning" %}
**Pre-routed traces on internal layers**\
If your input file includes pre-placed copper traces or pours on internal layers and you have _not_ selected to preserve the stack-up in your input file, Quilter will delete them and generate new ones for each candidate and layer stack it explores.
{% endhint %}



### Why should I pre-route traces?

There are a couple of reasons to pre-route components:\


1. **Unsupported physics constraints**\
   If Quilter doesn't yet support a physics constraint that needs sensitive or highly organized signal routing, you can manually pre-place and route individual components to ensure they work correctly. \

2. **"Saving your progress"**\
   When iterating with Quilter, you might find that you like certain parts of a layout candidate, but not the overall design. Once you've downloaded a candidate, you can choose to keep the routing and placements you like, remove the rest, and resubmit to Quilter to save your progress toward a fabrication-ready design.



### How to specify

Locking the path of a copper trace is easy – just pre-route it within the board outline and upload your input file to Quilter.&#x20;
