the old fashioned car wash... because a lot of horse muck was getting stuck to the bottom of cars in the 1920's

above is an Autowash Bowl in Chicago 1924 http://justacarguy.blogspot.com/2009/07/lost-to-yesteryear-only-known-to-us-by.html

The Neway Auto Wash Bowl was built in Chicago in 1924 by The Neway Auto Cleaning and Service Corp. The car was first run around in the pool of water to flush mud and dirt off of the undercarriage. It was then driven up into a stall and the car was washed in the normal matter to complete the job. 300-310 South Federal Street

above is from http://thiscircularparade.com/2012/02/14/a-novel-concept-for-a-car-wash-focused-on-cleaning-the-undercarriage/