3M Fire Barrier Moldable Putty+ is an intumescent fire-resistant putty that expands when exposed to heat. It is used to seal openings and maintain the fire rating of structures. The putty comes in stix, pads, and cable wraps and adheres to many surfaces. It has a four hour fire rating and expands to form an insulating char when heated, helping prevent the spread of fire and smoke. The document provides instructions on installing the putty in various applications such as sealing cables penetrating walls.