Lein, by definition, refers to the legal capacity bestowed unto a creditor to sell a debtor's property if they are unable to meet payments on a loan.
It is essentially used as means of reassurance of security for the creditor. For example, the bank can issue a lein mark on behalf of the creditor, i.e. Freeze the money, until the contractual obligations of the debtors loan have been fulfilled. In other words, the creditor does not lose their money until they are certain that the money can be repaid. This allows them the assurance to carry out loan arrangements.
This also entitles the bank to seize the property of the debtor, so long as reasonable notice is provided. However, a lein mark is not applicable when a property is in the banks possession for specific reasons, e.g. Temporary placement.
I hope this answers your question.