Erroneously making "refer" agree with plural sujects

I've seen this many times in WIkipedia articles, and even corrected it a few times. Last night I heard it in a YouTube video:

> The metal fittings **refer** to the various small metal items that anchor the toilet, connect it to the plumbing, and do the actual flush.

Metal fittings don't have the ability of referring to items. Words can refer to items. The correct way to write this is to quote the subject and then the quoted phrase is grammatically singular, no matter whether what the phrase describes is semantically singular or plural:

> "The metal fittings" refers to the various small metal items that anchor the toilet, connect it to the plumbing, and do the actual flush.

In this case the sentence still reads awkwardly so this isn't a complete fix. On Wikipedia it's usually done by people with poor English trying to copy the formulaic sentences used to commence many Wikipedia articles without understanding the subtleties.

Let me try to find some examples from Wikipedia:
- In an archaeological or epigraphical context, ostraca **refer to** sherds or even small pieces of stone that have writing scratched into them.
- IC codes **refer to** a police officer's visual assessment of the ethnicity of a person, and are used in the quick transmission of basic visual information, such as ...
- Calls for the destruction of Israel **refer to** expressions that call for the elimination of Israel as a modern country
- Common arguments for modal realism **refer to** their theoretical usefulness for modal reasoning and to commonly accepted expressions in natural language that ...
- The George S. Patton slapping incidents **refer to** two events that involved U.S. General George S. Patton and happened during the Allied campaign in Sicily ...
- Iraq–Israel relations **refer to** the bilateral ties between the State of Israel and the Republic of Iraq.
- Terminal Values **refer to** desirable end-states of existence.
- Afro-Turks, in Turkish Afro-Türkler, also named as Araplar or zenciler, **refer to** Black people of Turkish citizens whose ancestors once came to the Ottoman ...

There are of course legitimate examples on Wikipedia too:
- The terms Black Madonna and Black Virgin **refer to** statues or paintings in Western Christendom of the Blessed Virgin Mary and the Infant Jesus ✅
- Likewise, biochemical terms such as proton pump and proton channel **refer to** the movement of hydrated H+ ions. ✅
- The terms "red pill" and "blue pill" **refer to** a choice between the willingness to learn a potentially unsettling or life-changing truth. ✅
- Wets and dries are British political terms that **refer to** opposing factions within the Conservative Party. ✅

While looking for examples I found related misuses of "refer to" that are not the problem described in this feature request:
- Neolithic Italy **refer to** the period that spanned from circa 6000 BCE, when Neolithic influences from the east reached the Italian peninsula and the surrounding ...

Start by reviewing Harper's existing grammar-checking rules and how they distinguish valid plural subjects from agreement errors. Use the Wikipedia examples in the issue as cases to compare, including both the reported misuse and the legitimate uses of plural “refer to.” Done means the checker identifies the described misuse without flagging valid examples.

Written by the indexing model from the issue text.