- Covered in ferrous metal - Dressed in armour that is watertight? - Inflexible, rigid - Unbreakable (agreement) - Watertight - Clad in iron; protected or covered with iron, as a vessel
for naval warfare. - Rigorous; severe; exacting; as, an ironclad oath or
pledge.
- Crim at heart? Dig up stiff - Drilling platform identity card is inflexible - Frozen solid - Immobile - Inflexible - Inflexible or strict - Not pliant or flexible