||This article has multiple issues. Please help improve it or discuss these issues on the talk page.
Bondo is a brand of two-part putty manufactured by 3M. In 1955, the first batch of Bondo was made by mixing talc and polyester resin in an old dough machine. Later that year, the Bondo body-filler was born. Though originally used mainly for automobile body repair, Bondo is also widely used by carpenters for repairing wood defects. The Bondo brand of filler or putty is composed of a polyester resin. When the resin is mixed with a hardener (an organic peroxide) or catalyst, it turns into a putty, which then sets and hardens. The user can apply the mixed Bondo body filler, sand it to the proper shape, and prime and paint it like the surrounding material. The term "Bondo" is a registered trademark in the United States and in many countries throughout the world.
Bondo body filler was developed as a replacement for body solder, or molten lead, that was formerly used for the same task. Body solder is much more durable, but may require more effort to apply. Lead-based solder poses toxic hazards for people and the environment due to the heavy metal components. Although Bondo body fillers and other polyester body fillers are far safer to work with than their lead-based counterparts, they can still pose significant health risks. The fumes are quite toxic, and the hardeners can create burns on prolonged skin contact. The use of gloves, a mask, and proper ventilation are all recommended when mixing and applying the filler.
When buying a used car, it is possible to check for damaged areas that have been repaired with significant amounts of body filler by walking around the car with a magnet, as the magnet will not be attracted to the body filler. Unscrupulous sellers may mix metal flakes into the body filler mixture before application in order to circumvent the magnet test. This test however, will not detect body filler on plastic, fiber glass, or carbon fiber components.
Home and hobby 
3M also distributes Bondo "All Purpose Putty" which may be used on, but not limited to, wood, asphalt, masonry, metal, drywall, and tile.
Bondo fillers have widespread usage in computer case modding, as when properly used, they can be sanded smooth and painted, and they will attach and hold, without damage, to metal, plastic, acrylic and perspex (plexiglass) surfaces.
During the 2010 Daytona 500, a pot hole formed in the race track. After a concrete patch disintegrated, NASCAR used Bondo body filler to patch the track with just 40 laps remaining. The Bondo body filler held until the finish.
Bondo is portable. It can be mixed on site, and it hardens in a half hour or so, making it an ideal material for skateboarders to fixing cracked skating spots. However, this should never be done without obtaining permission from the property owner, as Bondo is difficult to remove and may make it more difficult to perform a proper repair.
Bondo can also be used to harden paper crafts and make props for cosplay or costuming.
Bondo brand fiberglass fillers are used in the marine industry. A glass-reinforced filler, resin, resin repair kit, and long-strand glass hair are the types of fillers manufactured.
Additional sources 
- Auto Body Repair Technology - James E. Duffy, Robert Scharff - Google Books
- The Ultimate Hot Rod Dictionary: A-Bombs to Zoomies - Jeff Breitenstein, Troy Paiva - Google Books
- Metal Casting: A Sand Casting Manual for the Small Foundry - Steve Chastain - Google Books
- http://solutions.3mcanada.ca/wps/portal/3M/en_CA/Bondo/Home/Resources/FAQ/ Where Do You Use Bondo Products? FAQ from the 3M website