Abstract: A collating apparatus is mounted above a copying machine and includes a housing frame enclosing a conveying mechanism for conveying sheets from the copy-ejection part of the copying machine along a vertical path alongside of which are positioned horizontal trays for receiving the copy sheets as collated. The trays have associated therewith guide elements which are balanced in equilibrium in a first position in which they project into the conveying path to guide sheets into their corresponding trays and which are activated by the receipt of a sheet in the tray to a second position in which they are moved out of the path. The guide elements are locked in this second position by pawl-like locking elements until all locking elements are released by an unlocking means activated by the copy machine start button.