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]
(..) Thanks. Alright, um, now then, remember, just because you made the team last year does not guarantee you a spot this year. Is that clear? Good. No hard feelings, Weasley, alright? (..)2009 Harry Potter and the Half-Blood Prince