3.7 | 6 Votes
What is a JMF file?
Native project format created by Jackhammer, a level and map editor for games with quake-style BSP architecture; stores a level and all related information, which includes map sources.
You should save your level in Jackhammer in the JMF format. Use the RMF format to export your map from Jackhammer to the Valve Hammer Editor.