Oakum
Oakum can be used to seal cast iron pipe drains. After setting the pipes together, workers pack oakum into the joints, then pour molten lead into the joint to create a permanent seal. The oakum swells and seals the joint, the "tar" in the oakum prevents rot, and the lead keeps the joint physically tight.
Today, modern methods, such as rubber seals (for example, gaskets or o-rings) are more common.
Stain-blocking primer
Stain-blocking primers are used to cover stains such as watermarks, nicotine (actually tar), markers, smoke, and prevent them bleeding through newly applied layers of paint. They also provide adhesion over problematic surfaces, giving better film leveling, and durability. Commonly used stain-blocking paints include acrylic and alkyd.