Answer:Attestation
Explanation: Attestation refers to how one attend an execution of a document and act as a witness to the authenticity of that document by signing that document to actual confirm that it is real or genuine
A custodian can sign such a document to say that this document is genuine
In attestation a witness declares that the action was carried in front of him and he knows all the formalities written in that documents.
It is used to make a will or deed valid.