copper bottom
/ˈkɑpər ˈbɑtəm/
verb
- To make something secure, reliable, or trustworthy, as if covering the bottom of a ship with copper to protect it.
- She copper-bottomed the deal with a signed contract and a deposit.
- To copper-bottom your investment, you should diversify your portfolio.
- The company copper-bottomed its reputation by offering a lifetime warranty.