Purpose
Chop shops are useful for earning money and disguising your cars. They will take any car you bring into the shop and change its appearance so that it can be sold as a different car. They will also change the appearance of your car if the cops are after you and you need to escape in a different car.
Shops
There are three chop shops in "Saints Row." One is located in Filmore, in the Downtown District. Another is located in the Chinatown District of Chinatown. The other one is located in Charleston in the Docks and Warehouses District.
Activities
Chop shops also have various activities that you can do. These resemble mini-games and let you earn more money. The games range from demolition derbies to taking hostages, driving a taxi and even assassination missions.