Proofreading is an iterative process of comparing galley proofs against the original manuscripts or graphic artworks to identify transcription errors in the typesetting process. In the past, proofreaders would place corrections or proofreading marks along the margins. In modern publishing, material is generally provided in electronic form, traditional typesetting is no longer used and thus (in general) this kind of transcription no longer occurs. Consequently the part played by pure proofreaders in the process has almost vanished: the role has been absorbed into copy editing to such an extent that their names have become interchangeable. Modern copy-editors may check layout alongside their traditional checks on grammar, punctuation and readability. A "galley proof" (familiarly, "a proof") is a typeset version of copy or a manuscript document. It may contain typographical errors ("printer's errors"), as a result of human error during typesetting. Traditionally, a proofreader looks at an portion of text on the copy, compares it to the corresponding typeset portion, and then marks any errors (sometimes called "line edits") using standard proofreaders' marks. Unlike copy editing, the defining procedure of a proofreading service is to work directly with two sets of information at the same time. Proofs are then returned to the typesetter for correction. Correction-cycle proofs will typically have one descriptive term, such as "bounce", "bump", or "revise" unique to the department or organization and used for clarity to the strict exclusion of any other. It is a common practice for all such corrections, no matter how slight, to be sent again to a proofreader to be checked and initialled, thus establishing the principle of higher responsibility for proofreaders as compared to their typesetters or artists. "Copy holding" or "copy reading" employs two readers per proof. The first reads the text aloud literally as it appears, usually at a comparatively fast but uniform rate.