AC/DC released "Hard As A Rock" in 1995 off their album Ballbreaker. It became their second #1 on the Album Rock Tracks chart.
Its another song where AC/DC took a page out of Chuck Berry's playbook of obscure sexual references. Chuck Berry was the master of making sexual references sound innocent. In the song "Hard As A Rock" AC/DC lead singer, Brian Johnson, sings about a woman who turns the guy on so much he becomes "hard as a rock." So maybe not so obscure after all.
AC/DC "Hard As A Rock" 1995