Yes, it should be harder than steel.
No other foundation than Jesus.
They explained the relationship between husband and wife as a base of a triangle, and the tip of the triangle as God.
When the husband and wife is anchored on God, as they move closer to the Father, their distance as husband and wife also shortens.
So, the more one knows the Father, the more attuned he/she is to his partner as well.
i'd be editing this post soon given more time...