The U.S. Fish and Wildlife Service in South Dakota has been experimenting with a tractor-towed machine that creates black lines which can be put in prior to a prescribed fire. Black lines, a relatively narrow strip of burned vegetation along the perimeter of a planned prescribed fire project, can make the ignition and holding of the main burn go much more quickly and also reduce the chance of a slop-over.
The device uses propane burners in a metal enclosure to burn the ground fuel, while water nozzles on the sides create a wet line to keep the fire from spreading. This
toy tool looks like it would be fun to play with.