How to make a schedule that filters on geometry without a material?

[semi]

Hi all,

how can I make a material take-off which shows me every geometry without a material.

For example I want to filter every column in my project where it says Structural Material "By Category"

[barthbradley]

BY CATEGORY doesn't necessarily mean the element has no material. It just means the element is using the Material assigned to the element's Category under Object Styles.  I'm not sure what the purpose is for scheduling this, but maybe open your Object Styles dialog box and assign the "Default" Material (or maybe a material named "NO MATERIAL") to every category that has "no material". Then create a MTO and filter out everything but the "Default" (or "NO MATERIAL") Material.  

[semi]

The reason for this is to check which families in the project don't have a material assigned to it. 
If no material is assigned to certain families they don't show up in their schedules for keynoting.

For example: a steel beam with steelgrade S355 should have that particular keynote material to refer to our specifications 

[barthbradley]

Why don't you just assign a Material to the Structural Framing Category under Object Styles?