Corrections to a text were undertaken by the scribe, another member of the scriptorium , a stationer, an owner, or a subsequent reader. They take various forms, including simple interlinear or marginal insertions (perhaps marked by a signe-de-renvoi), erasures made by scraping with a knife or pumice (or washing, in the case of papyrus), cancellations indicated by crossing out, or expunctuation (in which points placed beneath a letter or word mark its deletion). Some corrections resulted from a systematic program of comparing a text against another copy; others represent the independent decision of a scribe or reader to amend words or passages. The process of correction frequently formed part of the production of a manuscript.