GerbMerge is a program for combining (panelizing) the CAM data from
multiple printed circuit board designs into a single set of CAM files. The
purpose of doing so is to submit a single job to a board manufacturer,
thereby saving on manufacturing costs.

Advice: "Users of GerbMerge complain that the configuration file is the
biggest hurdle to overcome in using the program. Don't panic. Start with
a sample configuration file and modify it for your own jobs".