The common house rat or “Roof Rat” is about 20 inches (50 cm) long and weighs approximately 12 ounces (0.34 kg). Rats are famous for being able to chew through things—soft concrete, wood, plastic, aluminum, and cinder blocks are no match for these rodents. Their love of chewing is due, in part, to the fact that their teeth never stop growing. In order to keep them from becoming too long, making eating impossible, rats must constantly gnaw to wear down their teeth.
Worldwide, rats and mice spread over 35 diseases. These diseases can be spread to humans directly, through handling of rodents, through contact with rodent feces, urine, or saliva, or through rodent bites. Rats are some of the most troublesome and damaging rodents in the United States. They eat and contaminate food, damage structures and property, and transmit parasites and diseases to other animals and humans.  These rodents live and thrive in a wide variety of climates and conditions and are often found in and around homes and other buildings, on farms, and in gardens and open fields.  If you notice rat damage or see droppings, consider checking your entire property for other signs of rats. 
When food, water, and shelter are available, rat populations can increase quickly. While the most permanent form of control is to limit food, water, shelter, and access to buildings, direct population control often is necessary. Trapping is an effective method for controlling rats in and around homes, garages, and other structures. Because snap traps can be used over and over, trapping is less costly than poison baits. Traps can be set and left indefinitely in areas such as attics where rats have been a problem in the past. The simple, wooden rat-size snap trap is the least expensive option, but some people prefer the newer plastic, single-kill rat traps, because they are easier to set and to clean.
A rodent like a rat or mouse will leave several visual cues that they have made your home, apartment or business its new home. One of the first visible signs of a rodent infestation is droppings. Droppings are dark pellets often deposited where rodents are traveling and feeding. These droppings must be removed and the surface quickly disinfected due to the bacteria and disease they can spread. They are also another way to determine if you have a rat or mouse. Mice will leave small rice-sized droppings where as rats leave larger ones.