Accessus is a term applied to the voting in conclave for the election of a pope, by which a cardinal changes his vote and accedes to some other candidate.
Election by accessus was only possible because, until the mid-20th century, the ballots used by each cardinal were identified by a text of scripture in the back side.
When a cardinal decided to use the right of accession, his two ballots had to "be compared and identified by the text on the reverse face of the ballot, so as to prevent a double vote for the same candidate by any elector".
[3] Thus, voting by accession eliminated the secrecy of the first ballot.
Voting by accessus was prohibited by the Cardinal Dean at the 1903 conclave and later this form of election was suppressed from the Catholic Church's legislation.