What are water plugs for a dodge neon?

these metal plugs can seen in places on cyl head , blocks. there part of casting process during manufacture of blocks or heads allow core sand forms held while pouring molten metal in casting , allow removal of sand afterwards.
not pop or blow when engine gets hot cold unless water in block frozen ice when water expansion can dislodge them.
can rust internally , pinhole showing antifreeze stains , residue dries around leaking joint etc.
if these starting leak? due wrong or insufficient anti freeze being used allowing corrosion occur. replacing engine out job due access issues.

i have dodge neon 2004 , person looking @ said needs water plugs i've never heard of water plugs can tell , show me , worth fixing or should let go?

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