Komentarz do Diwrej ha-jamim II 3:5

and he overlaid it with gold i.e., When he made all the decorations, he overlaid the walls with gold after the decorations, and he reinforced them with nails in the wooden wall, in order that it should not move; which is something that he could not do on a stone wall. For this reason, he overlaid the entire House with juniper wood.

and chains He made many decorations, filling it completely, and when he saw that there was any blank space between one decoration and another, he painted a decoration like a sort of chain, with which things are connected, so did he do here between one decoration and another, in order that there should be no blank space in between. Another interpretation is that he made real golden chains and connected the shapes together with them.