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.
Dental dam
A dental dam or rubber dam (sometimes termed "Kofferdam"—from German), designed in the United States in 1864 by Sanford Christie Barnum, is a thin, square sheet, usually latex or nitrile, used in dentistry to isolate the operative site (one or more teeth) from the rest of the mouth. It is used mainly in endodontic, fixed prosthodontic (crowns, bridges) and general restorative treatments. Its purpose is both to prevent saliva interfering with the dental work (e.g. contamination of oral micro-organisms during root canal therapy, or to keep filling materials such as composite dry during placement and curing), and to prevent instruments and materials from being inhaled, swallowed or damaging the mouth. In dentistry, use of a rubber dam is sometimes referred to as "isolation".