A method for locally reinforcing or baffling a structure having a hollow cavity is disclosed. The present invention provides an insert that includes a carrier, a thermally expandable material located on at least a portion of the carrier, and at least one integrally formed attachment that projects outwardly from the carrier. The inserts of the present invention are preferably placed within a hollow cavity in a transverse direction so that once the insert is sealed into place via the thermally expandable material, the hollow cavity is separated into two separate chambers.