When attacking the castled king, it is helpful to look at the enemy pawn structure and imagine all enemy pieces off of the board, leaving only the pawns. Where the pawns are advanced, you can attack and fill in the holes with your pieces. When taking into account the pawn structure holes, it is helpful to know basic checkmates on the enemy king. Here are some.
Notice how one piece is used to set up a barrier once the pawn hole has occurred.
The bishop sets up the barrier and
protects the rook.
The bishop sets up a barrier
and protects the queen.
The bishop sets up the barrier and
the knight checkmates.
The knight helps set up the
barrier and protects the rook.
The queen sets up the barrier and
the knight checkmates.
The black bishop sets up the
barrier and the white bishop
checkmates.
The king sets up the barrier and
the rook checkmates.
Remember: