# Pre-routed traces

### Overview

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

**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. 

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:<br>

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. <br>
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;


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