# Overview **Design Parameters** are key design considerations that determine the options available to Quilter when generating layout candidates. These parameters cover everything from high-level questions, such as *who will manufacture your board,* to low-level details, like *where to place a capacitor.* Once your board's Design Parameters are fully defined, your layout candidate is complete. Your input file is the main way to tell Quilter which Design Parameters (design elements) are fixed and which remain flexible for Quilter to explore. We typically categorize Design Parameters into three main groups: 1. **Fabrication parameters** – who will manufacture your board, and what fabrication capabilities and materials do they have? 2. **Placement parameters** – where do components go on your design? 3. **Routing parameters** – how should components be connected? As mentioned in [our introduction](https://docs.quilter.ai/using-quilter/select-your-stackup), Design Parameters can be either requirements that Quilter *must* follow or *preferences* that act as filters on the solution space Quilter explores. Check out the tables below to learn how to control Quilter's options and key parameters of the candidates it generates. ### Fabrication In a traditional design workflow, fabrication parameters are fixed before the design process starts. Quilter reverses this approach, allowing you to consider the fabricator, fabrication rules, and even the stack-up as variables within the solution space that Quilter can explore and optimize. By switching fabrication parameters from constraints to optimization variables, you can do amazing things with Quilter, including: 1. **Compile for multiple fabricators.** Create a single design that can be compiled for multiple fabricators and stack-ups, then send it to the manufacturer with the lowest cost or fastest turnaround time. 2. **Analyze performance vs. speed and cost.** Compile the same design with different fabrication rules (3.5 mil, 5 mil, and 6 mil) to explore the trade-offs between physics performance, layer count, and fabrication cost/speed. 3. **Optimize board density.** Compile the same design with various board outlines to examine the relationship between board size, component density, and layer count/routability.

Parameter	Description	Preference	Requirement
fabricators	The PCB manufacturer that a specific layout candidate (stack-up and fabrication ruleset) is designed for.	✅ Filter by fabricator	✅ Enteprise customers only
stackups	The stack-up that Quilter uses when generating your candidate, including layer count, copper weight, material properties, and more.	✅ Layer count only	✅ Stackup from input files
fabricator-constraints	Basic design rules that ensure your board can be manufactured without issue – trace, space, drill, via, edge clearances, etc	✅ Trace and space	✅ Design rules from input files

### Placement Placement parameters let you control where Quilter places components on your board, ensuring the layout candidates it generates meet your design requirements and preferences. Specifically, you can use placement parameters to: 1. **Restrict placement to one side** for easy assembly and testing 2. **Enforce a specific "floor plan"** that meets 3D spatial requirements and signal flow 3. **Lock components** in place during iterations so that you can save your work throughout the design process

Parameter	Description	Preference	Requirement
pre-placed-components	Lock the location of location-sensitive components so Quilter can't modify it.	⬇️ Use "placement regions"	✅ Place within board outline in input file
placement-regions	Restrict Quilter's placement of unplaced components to a designated area within your board outline.	❌ Placement regions are always respected	✅ Add to input board file
single-sided-placement	Limit placement to one side of the PCB.	✅ Filter for single-sided designs.	⬆️ Use "placement regions"

### Routing Routing Parameters help you influence and control how Quilter implements your board's netlist, to ensure that the layout candidates Quilter generates meet all of your electrical requirements and preferences. Routing parameters can be used to: 1. **Define a custom stack-up** that includes power planes dedicated to specific nets within your design (coming soon) 2. **Assert custom net widths** for specific nets or net classes to override or supplement the [fabricator-constraints](https://docs.quilter.ai/using-quilter/fabricator-constraints "mention")for a particular layout job 3. **Lock routing strategies** during iteration, so you can "save your work" throughout the design process

Parameter	Description	Preference	Requirement
pre-routed-traces	Lock the routing path of sensitive signals.	❌ Pre-routed traces are always preserved	✅ Leave within board outline in input file
preserved-pours	Preserve existing copper pours from your input pile for Quilter to use when generating candidates.	❌ Preserved pours are always respected	✅ "Lock" pours you want to preserve in input ful
keepouts	Prevent Quilter from routing traces through specific geometric areas within your design.	❌ Keepouts are always respected	✅ Add keepout to your input file
net-widths	Manually specify net widths for individual nets or net classes in your design.	❌ Net widths are always respected	✅ Specify "Net Width" in during job setup