The software comes with a 'money-back guarantee'. [=a promise that the money you spend on a product will be returned if the product is not good enough]
We used our house as a 'guarantee' for the loan. [=we said that the bank could take our house if we did not pay back the loan]
There is no 'guarantee' that they will approve the contract. [=there is no way to be sure that they will approve it]
(..) I should've realized then, That they were a surgical experiment. To see if it's possible to make one man look like another? His face is no longer his own. What better way to guarantee his world war than to make the assassin... One of the ambassadors. That narrows down the possibility to one of six. (..)2011 Sherlock Holmes: A Game of Shadows