The second generation of Leatherman multi-tools introduced a diamond file with a standard metal/wood file on one side, and a diamond-coated file on the other side. This tool replaced the regular metal file/saw.
Use the standard, grooved part of the file when working on soft materials (including wood, copper, and brass). The diamond-coated part of the file works well on any type of hardened steel, cast iron or alloy. It's particularly good for sharpening fish hooks, and the 420HC stainless steel alloy used on most other Leatherman tools. You can also use the diamond file on ceramics, glass, or any other hard material, though they will wear the tool much more quickly than softer materials.
Use light force when working with the diamond blade so you don't scrub off the diamonds, and this tool will give you many years of service.
Many Leatherman tools have a standard metal file and saw.
There are no diamond-based tools on Victorinox or Wenger Swiss Army knives.