Skärbord
The SkärBord is simply the best tool for cutting insulation, and the only tool you need if you are indeed serious about good insulation installs. There is no faster, more accurate, or easier way to install mineral wool insulation and interior sound batts. And the SkärBord is effective for cutting a range of other insulation types as well: fiberglass, foam, and wood fiber insulation panels all benefit from the speed and accuracy that comes from working with the SkärBord.
SkärBord allows you to make angles cuts, narrow cuts, and as well as cut multiple layers at one time.