Rats in abandoned piping
Upon arrival a clients home I find she has rat droppings not mice. Downstairs I find a septic stack with a long elbow which is opened up on one end which used to service an abandoned toilet no longer in use. The end was capped and I even took a photo of the droppings inside with my snake scope camera. Rat issues can be simple or complex in this case her basement was open so that a quick observation could be made based on experience I could narrow the problem down quickly.