In my personal transactions, the word “Vouch” means that you guarantee that the borrower has sufficient assets to repay that loan or has family/friends/acquaintances who can repay that loan. Therefore, if a problem occurs and the loan is not repaid, you can force him to sell those assets or talk to others to repay the debt for him.

In short, it is your responsibility to make him pay the debt, whether directly or in installments.