Words in a deed or other document written on erasures, are taken pro non script-is, but if in a material clause, they may vitiate the whole document. When words are purposely erased, the fact, and the number of the words erased, must be stated in the attestation clause. Words to be inserted must be written on the margin, and attested by the signatures of the parties, the Christian names preceding and the surnames following the marginal note.

Source: Kinnear, Digest of House of Lords cases (1865), pg. 354.