Hi Everyone. I have an 02 crv. I went to clean the VTech solenoid and replace gasket as I have a large oil leak there. Took the valve off and there were the usual openings there.. someone replaced it before I got the car. As I was putting it back together I noticed a rectangular hole right below it. The oil pressure sender is screwed into this channel a little lower down. What is this and what do I do about it?

What's the rectangular hole for?

 

Artifact from casting the block. Normal and nothing to worry about.