In Part Design workbench, Insert a PartBody. Reorder your "Thick" surface after this new Part Body. Remove the new PartBody / Thich surface. Depending what children the Thick solid has, it may be necessary to reorder them too, to resolve Update errors.
Firstly, you may benefit from selecting features from the specificaiton tree, to be more "specific".
I have tried this to represent threads in 3D, and the easiest solution was to use a surface (Extrude circular profile in your case), then change the colour of the surface (again, selected in the...
