Car stops, also know as known as wheel stops or parking blocks, are the simple blocking mechanisms that are used to stop a vehicle from rolling forward when parked in a particular area. Similar to speed bumps in the way that they are made, car stops are usually taller and they have steeper sides. While speed bumps are meant to be driven over, car stops are actually meant to prevent a car from moving. Car stops can come in a variety of materials including recycled plastic, rubber, or concrete.