Bondo is a two-part putty used to fix dents in cars, created by Bondo Corporation. While the term "Bondo" is a brand name for this company's product, it is commonly used in the U.S. as a genericized trademark to refer to all auto-repair putties or so-called plastic body fillers. Bondo is a two-part polyester that when mixed turns into a putty which then sets and becomes rock-hard.