מלכים א ו:טו פירוש: רש״י

With panels of cedar. Boards of cedar against the stone wall in order to coat it with gold, as it states below, “And Shlomo covered the inside of the Beis Hamikdosh with refined gold,”²⁴Below, v. 21. and it is impossible to coat gold on top of the stones, without wood and nails.

Beams of the ceiling. The boards of the attic.

The floor of the Beis Hamikdosh. The entire floor.