A fender apron is a panel on the inside of the fender that prevents splashing water from reaching certain areas of the fender, wheel housing, and/or A-pillar. These are usually mounted in an upright position ahead of or behind the front wheels.

Driving through winter snow, ice, and rain means your car or truck is exposed to highly corrosive winter road salt, like it or not. And if you have any trouble guessing which particular area of your vehicle is most subject to rust, where slush builds up the most - wheel wells.

To contain this slush and prevent water, dirt, and other contaminants from being kicked up into your engine bay and trunk where they would have extremely negative effects, your vehicle manufacturer installed specially shaped liners on the inside of the fender wells. They're most commonly known as wheel well liners or inner fender panels.