I still don't understand what happens when you actually break something expensive that you hire? Doesn't some 3rd part have to verify the damage? Doesn't the 2

I still don't understand what happens when you actually break something expensive that you hire? Doesn't some 3rd part have to verify the damage? Doesn't the 2nd part then have to still take a part of the bond? What if the 2nd part just says you broke something, when you didn't, who solves that?