'Planks' or 'boards,' as in for the tabernacle, signify supports from good, because they were made of wood, and supported the curtains both of the tabernacle and the tent, as in Exodus 26:15-29. As far as all the representations in nature refer to the human form, and have significance according to that reference, and so they have the planks of the Tabernacle. These correspond to the muscles or flesh of a person, which supports the surrounding coats and skin.

(References: Arcana Coelestia 9634)