AFTER THE COPY HAS BEEN PREPARED and copy-read, it goes to the linotypist to be set into type: During this process the linotypist may commit any of the following errors:

1. Copy errors – These are errors in grammar and word omission that had escaped the blue pencil of the copyreader and which the linotypist copied verbatim.
2. Machine errors – These are errors made due to faulty typesetting machines like excessive transposition of letters, blurred letters, poor letter alignment, wrong font, and high or low slug.
3. Operator’s errors – These include the general run of typographical errors.

Thus, the need for speedy and accurate proofreading.