Definitely a guard. Used it to cut tile in places where wet cutting wouldn't work and would require hours of work and maximum disruption for a family of four to create an airtight barrier. With a zipper for some containment and a fresh filter and bag in my vacuum, I was able to cut with almost no residual dust. Since this determined where the hardwood would meet the tile, the line had to be very straight and the adjustable blade indicator did a great job.