Most Skimmer boxes are designed with the same major components
The lid & Dress ring sit on top of the pool surround while the rest is cast in to the concrete or block walls.
The Skimmer must be installed so that the center line of the mouth is 150mm (6") below the top of the pool.
Sometimes the pump connection is in the bottom & sometimes on the back at the bottom.
The main drain connection can be on the side as shown or through another connection in the bottom.
The vacuum plate is necessary for manual cleaning of the pool floor
The weir flap allows there to be a skimming action irrespective of the water level, (give or take 50mm, 2")