A guide apparatus for guiding sheets to a sheet-processing machine, in particular a printing machine, and a method of operating the guide apparatus are described. The guide apparatus has at least one guide element which is disposed above a feed table and whose distance from the feed table can be set with the aid of a height-adjusting device. The guide apparatus is distinguished by the fact that the height-adjusting device has a first drive and a second drive, which can be actuated independently of each other.