Abstract: In a door or the like having spaced-apart planar side panel members and baffle means intermediate the members, the baffle means comprises an elongated planar member secured to and extending from the respective side panel members such that the planar members lie in spaced parallel relation one to another and extend toward one another in overlapping arrangement and the free ends of the planar members terminate in spaced relation with the panel members. The improvement comprises the filler means intermediate the free ends and panel members whereby to provide a partially sealed cavity between the planar members. Also disclosed is a method of preventing or limiting deformation of a door panel when located adjacent fire in turn preventing or limiting deformation of the door edges affecting securement of the door.