Prevents waste of material, extra cleanup, or potential plant damage.
The side deflector takes the guess work out of gauging correct distance from driveways, walkways, landscape beds, and borders. Quickly flip down the spring loaded deflector to prevent spread of material beyond the right wheel.
After getting it installed it works well, instructions are not the best and be ready with the right tools. I consider myself pretty handy and it took some effort (and some cursing).