# Is it possible Dynamo make line as per duct size in revit
**URL:** https://forum.dynamobim.com/t/is-it-possible-dynamo-make-line-as-per-duct-size-in-revit/114796
**Category:** Revit
**Created:** [June 17, 2026, 10:30am UTC](https://forum.dynamobim.com/t/is-it-possible-dynamo-make-line-as-per-duct-size-in-revit/114796 "2026-06-17T10:30:14Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@yousuf5568](https://forum.dynamobim.com/u/yousuf5568)
#### Post date: [June 17, 2026, 10:30am UTC](https://forum.dynamobim.com/t/is-it-possible-dynamo-make-line-as-per-duct-size-in-revit/114796/1 "2026-06-17T10:30:14Z")
I want to create a script in Dynamo that draws a line in Revit based on a duct’s size, and also includes the system and size with it. When I export this to CAD, I want to be able to calculate the quantity using that line. Is this possible?.. i make a script but i am not able to complete. its showing errors please help.
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### Author:  [@Nick\_Boyts](https://forum.dynamobim.com/u/Nick_Boyts)
#### Post date: [June 17, 2026, 2:19pm UTC](https://forum.dynamobim.com/t/is-it-possible-dynamo-make-line-as-per-duct-size-in-revit/114796/2 "2026-06-17T14:19:02Z")
What does the warning/error say? This is totally possible using the methods you’ve shown.
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### Author:  [@yousuf5568](https://forum.dynamobim.com/u/yousuf5568)
#### Post date: [June 18, 2026, 6:24am UTC](https://forum.dynamobim.com/t/is-it-possible-dynamo-make-line-as-per-duct-size-in-revit/114796/3 "2026-06-18T06:24:35Z")
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### Author:  [@BimAmbit](https://forum.dynamobim.com/u/BimAmbit)
#### Post date: [June 18, 2026, 7:25am UTC](https://forum.dynamobim.com/t/is-it-possible-dynamo-make-line-as-per-duct-size-in-revit/114796/4 "2026-06-18T07:25:43Z")
Try removing the double quotes of **Duct\_Info** since it’s a String node.
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### Author:  [@yousuf5568](https://forum.dynamobim.com/u/yousuf5568)
#### Post date: [June 18, 2026, 7:46am UTC](https://forum.dynamobim.com/t/is-it-possible-dynamo-make-line-as-per-duct-size-in-revit/114796/5 "2026-06-18T07:46:05Z")
Same error is coming.
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### Author:  [@BimAmbit](https://forum.dynamobim.com/u/BimAmbit)
#### Post date: [June 18, 2026, 7:51am UTC](https://forum.dynamobim.com/t/is-it-possible-dynamo-make-line-as-per-duct-size-in-revit/114796/6 "2026-06-18T07:51:59Z")
Then I suppose you really don’t have a parameter named Duct\_Info. I would check the spelling of that parameter name, no extra space or anything.
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### Author:  [@yousuf5568](https://forum.dynamobim.com/u/yousuf5568)
#### Post date: [June 18, 2026, 12:25pm UTC](https://forum.dynamobim.com/t/is-it-possible-dynamo-make-line-as-per-duct-size-in-revit/114796/7 "2026-06-18T12:25:25Z")
I tried putting in a new parameter too, but the same error keeps popping up.
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### Author:  [@BimAmbit](https://forum.dynamobim.com/u/BimAmbit)
#### Post date: [June 18, 2026, 12:52pm UTC](https://forum.dynamobim.com/t/is-it-possible-dynamo-make-line-as-per-duct-size-in-revit/114796/8 "2026-06-18T12:52:54Z")
I’ve just noticed these are model curves. user-defined parameter cant be added to that category iirc. Off the top of my head, you can use duct placeholders or a custom line family to work around this. or by using Extensible Storage, but that’s a long story.
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### Author:  [@Nick\_Boyts](https://forum.dynamobim.com/u/Nick_Boyts)
#### Post date: [June 18, 2026, 2:37pm UTC](https://forum.dynamobim.com/t/is-it-possible-dynamo-make-line-as-per-duct-size-in-revit/114796/9 "2026-06-18T14:37:51Z")
> [@BimAmbit](#):
>
> user-defined parameter cant be added to that category
This is exactly correct. I missed that on my initial read.
You had the right idea, you just don’t have that parameter to write to (and you can’t assign model lines project parameters). One alternative would be to create a new `LineStyle` for every unique system and size in your project and just create the model lines using the appropriate `LineStyle`.
[NewSubcategory Method](https://www.revitapidocs.com/2024/aba44eba-9882-54cb-fe52-30553a684c34.htm)
You also might want to double-check what information actually gets exported to CAD with the model line. It’s probably been a decade since I’ve ventured into CAD. I have no idea what all transfers accurately.