Rock-solid (adjective)

Extremely reliable, dependable and sturdy.

Origin:

From the combination of the words "rock" and "solid".

Examples:

1. His reputation for being rock-solid made him the ideal candidate for the job.
2. The company's financial position was rock-solid and it had a good credit rating.
3. The rock-solid evidence made it impossible for the defendant to be acquitted.
4. His rock-solid support was crucial in getting the bill passed.
5. The rock-solid foundation of the building had stood the test of time.