According to my knowledge in the field of vocational training, the following transactions usually require customer signatures:

1. Contract signing: In business transactions, both parties usually need to sign a contract to ensure the legality of the transaction performance and enforceability. When customers sign a contract, they indicate that they agree to the terms of the transaction and are willing to conduct transactions in accordance with the contract.

2. Authorization: Certain transactions may require customers to sign an authorization to authorize others to perform certain specific actions on their behalf. For example, when purchasing real estate, home buyers may be required to sign a release authorizing the real estate agent to represent them in dealings with the seller.

3. Confidentiality Agreement: In transactions involving trade secrets or sensitive information, both parties may be required to sign a confidentiality agreement (also known as a confidentiality agreement or non-disclosure agreement). Clients signing non-disclosure agreements indicate that they will protect and keep protected information confidential and will not disclose it to unauthorized persons.

4. Consent Form: Certain transactions or activities may require customers to sign a consent form. For example, when participating in a certain sporting or risky activity, clients may be required to sign a consent form indicating that they understand and accept the associated risks and agree to voluntarily participate in the activity.

Please note that the above are just some common scenarios, and whether a specific transaction requires a customer signature may vary depending on industry and national laws. If you are involved in a specific transaction, please learn more about the relevant regulations and compliance requirements.