As a lawyer, I can advise you on the following ways to ensure your legal documents are airtight:

1. Review your legal document: Make sure that you have reviewed your legal document thoroughly before signing it. Ensure that it accurately reflects your intentions and has all the necessary parts to accomplish what you want.

2. Use unambiguous language: Your legal document should be written in clear and unambiguous language so that there will be no confusion over its meaning.

3. Seek legal advice: If you are not sure about the legal implications of your document, it's best to seek advice from a legal professional. Consult with a lawyer who specializes in the area of law that the legal document pertains to.

4. Consider all possible scenarios: Think about all possible scenarios that might arise in the future, and ensure that your legal document accounts for all of them.

5. Ensure all parties understand their obligations: Before signing the legal document, make sure all parties involved understand their obligations under the agreement.

6. Keep copies of your legal document: Make sure you have a copy of your legal document, and keep it in a safe place. This ensures that you can refer to it if needed, and also preserves a record of your agreement.

By following these tips, you can ensure that your legal document is airtight and legally binding.