Are you talking about Sheet Metal thickness? Unfortunately sheet metal cut-list properties cannot be propagated to SolidWorks properties by some reasons. The following won't be evaluated:
"SW-Sheet Metal Thickness@@@Cut-List-Item1@Part1.SLDPRT"
The Weldment Cut-List properties can be evaluated. For example this one will be successfully evaluated but none of SM properties:
Artem Taturevych, Application Engineer at Intercad (Australia)
translationXpert – add-in to translate SolidWorks models
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on my plate stock ive been using the bounding box deminsions to link everything. right click on the item you want and add bounding box. then go into the cutlist properties pick the part and add the property "thickness" and for the value copy and paste the bounding box thickness code ex. "SW-3D-Bounding Box Thickness@@@partname@testpart.SLDPRT"