signature
handwritten mark made as a proof of identity and intent
book signing
repeated affixing of a signature to the title page or flyleaf of a book by its author, often after an author reading or author discussion; for the reader, the signature increases the value of the book
builder's signature
tradesperson's signature on constructed project
countersign
addition of a second signature onto a document
countersign
addition of a second signature onto a document
file signature
data used to identify or verify the content of a file
autograph
hand-written signature of a famous person