PURPOSE: To reduce damage due to dew condensation by providing a trunk lid panel with a plastic corrugated cardboard of a high rigidity in such a way as it may be freely fitted and removed.

CONSTITUTION: When moisture in a trunk room 1 is cooled, waterdrops are frozen on the back of the truck lid 2 and a trunk lid trim 10. When this ice is warmed, it is melted into waterdrops which drop and are pooled in a concave 13 of the trunk lid trim 10 without trickling from the end of said trim 10. Waterdrops on a cloth material 15 are also frozen, however, after being melted into waterdrops again, they just soak into the cloth material due to its surface tension and a capillary phenomenon only to evaporate as the interior of a room 1 becomes dry. Use of a hollow plastic corrugated cardboard as the trim 10 improves adiabatic effect remarkably.