Final answer:
Pencil-like stools are typically a sign of an obstruction in the rectum, which is the latter part of the colon.
Step-by-step explanation:
Pencil-like stools can occur when there is an obstruction in the rectum. The rectum is the last section of the colon where waste material is stored before it leaves the body through the anus. Due to its position in the digestive tract, a narrowing or blockage here can cause stools to become thin and pencil-like. Obstructions can be caused by various factors such as tumors, inflammation, or scar tissue. It is essential for anyone experiencing a persistent change in their bowel habits, like the development of pencil-like stools, to seek medical advice.