Stacking allows you to multiply (or “stack” ) the amount of uninsured/underinsured motorist coverage by the number of vehicles on your policy. If you had 2 vehicles, you would have twice as much uninsured/underinsured motorist coverage, per vehicle, if you chose Stacked. It costs extra to stack uninsured/underinsured motorist coverage. If you own only one vehicle, then Stacking does not apply.