Slice Off Faces can be used only on Solid body.

Internally the Slice Off Faces option is very similar to Face Delete. In Face Delete, the selected faces are removed from the model and deleted. Afterwards, the engine will attempt to heal the remaining bodies. In Slice Off Faces, the selected faces are also first removed from the existing model, only then they are not deleted, but rather, Ansys DesignModeler will attempt to create new bodies out of the sliced-off faces. An important similarity between Slice Off Faces and Face Delete is that both operations involve model healing, and the engine may not be able to determine a suitable extension to cover the wound left by the removed faces. If so, then the feature will report an error stating that it cannot heal the wound.

Other Slice feature options: