Bolt Thrower

Models with this special rule count as having Defense 2+ against all shooting attacks.

Units with this special rule may never move regardless of which action they take and they can’t take Charge actions.

Models with this special rule must accumulate X wounds before being removed as a casualty.

If a model with Tough joins a unit without it then you must remove regular models as casualties before starting to accumulate wounds on the model with Tough.

When a unit with multiple Tough models takes wounds you must accumulate them on a single model until it is killed before starting to accumulate them on another.