To speed up clothes drying and prevent lint build-up, install a smooth metal dryer vent. These step-by-step directions walk you through the tough parts. Rigid metal vents are safer than flexible plastic and metal types, which catch more lint, require more cleaning and can retard airflow. Even worse, flexible ducts are easily crushed, which blocks airflow and causes the dryer to overheat, which in turn can lead to lint fires. In this story, we’ll show you how to cut and install 4-in. rigid metal duct, including the toughest part—drilling the exit hole through an exterior wall.