Sentence:  He invented the grooved wood roll or mandrel on which the thin film of wet paper, as <WSD>couched</WSD> from the cylinder mould, was wound and thus the sheet built up to the required thickness, when it was cut from the roll or mandrel along the groove and peeled off to be air dried and sheet calendered. 
Meaning of the word marked with <WSD> tags:  To transfer (for example, sheets of partly dried pulp) from the wire mould to a felt blanket for further drying.