As rats move about their nest site, they establish paths that they will use these paths faithfully. They have created these paths because they lead to areas where they forage for food. When someone has the proper knowledge, they will know what to look for and how to find them. They are easiest to see in muddy or dusty areas and their tracks can easily be seen in these areas as well. They have 4 toes on their front feet and 5 toes on their back feet. Their tracks are going to be all over these paths and they can help to identify a rat problem.
There will be other signs around their paths that will let a trained eye identify their presence. Because of their constant chewing, there will be chew marks around these established paths. They have to chew because their front teeth are always growing, and the chewing is their way of keeping them at a manageable size. They are also going to leave behind urine and droppings and their most used paths are going to have more signs of their presence. This identification may require the help of a professional because their footprints can be confused with other animals (such as squirrels) or if a homeowner is just not sure what it is they are looking for.