A letter of guarantee without signature is an invalid book, and a contract is legally binding. It will take effect only after both parties agree to be present and sign for notarization. Generally speaking, contracts that meet the following conditions will take effect:

1, the parties to a contract have the corresponding ability to conclude a contract;

2. The intention of the parties to the contract is true and both parties need to sign it;

3. The contents of the contract do not violate the provisions of laws or social public interests;

The content of the contract must be determined.