Abstract: A low profile heat sealing iron for use in applying heat activatable tape in areas of very limited access, such as the sealing of periodic joints in air duct is disclosed. The low profile sealing iron requires only a few inches or less of clearance and has a tape guiding means that feeds the tape to the proper location for heat sealing as the iron is slid along the surface of the member on which the tape is being applied. Preferably, the iron has a handle of adjustable length which permits the sealing iron to be used on ducts measuring six to eight feet or more when the handle is extended, but having a handle only about three feet long or less for easy carrying and handling at other times. A method of using the low profile sealing iron to seal joints in air ducts is also disclosed.