Be like/as safe as Fort Knox adjective
The mansions of almost billionaires are like Fort-Knox because there are plentifully valuable assets inside their house.
About money matter, my mom is as safe as Fort Knox.
Political figures often like to stay in a strongly built and well-protected houses which are as safe as Fort Knox because their lives are often threatened by many factions and parties.
To save someone from trouble, difficulty, or danger that is going to happen very soon
Protect one from harm caused by unforeseen events
1. Used to indicate an extra seat or portion of the main seat of a motorcycle meant for a passenger (traditionally occupied by a woman).
2. Used to say that a protective pad is worn on the groin area to protect it during sporting events and is usually worn by women.
3. Used to indicate that a pad is used with a barbell during squats to give cushioning and support to one's neck, so-called because it is looked down on by some as being unmanly to use.
To protect or express one's support for someone or something.
To keep watch or act a guard for someone or something.
Image source: Slideserve
The idiom originates from a real military place in Kentucky, which called Fort Knox. This place stores gold, therefore, it always safeguarded.