Abstract: A system for trimming, insulating and sealing between two separate elements of a building structure. The system includes an elongated strip of material, such as wood, having a channel on its reverse side which is wider than the width of a gap in the building structure which is to be covered by the strip. A compressible insulant, such as foam, is disposed in the channel and, like the channel, has a width greater than the width of the gap so that the insulant seals between the two building elements when the strip is installed. The insulant extends outwardly from the channel so that it is compressed when the strip is installed.