A clay block for car washing is a detailing tool used to remove contaminants and restore smoothness to the paint surface of a vehicle. It is similar to a clay bar but comes in a block form, making it easier to hold and use compared to the traditional clay bar. The clay block is designed to glide over the surface of the car, picking up dirt, grime, and other contaminants that have bonded to the paint. It helps in achieving a clean and smooth finish on the car's exterior by removing embedded contaminants that regular washing may not eliminate. Clay blocks are reusable and come in different grades to suit various detailing needs.