Come learn 2000+ kanji and 6000+ vocabulary words with WaniKani.
To Make Sure Of
To Verify, To Confirm, To Make Certain
transitive verb, ichidan verb
Like with 確か, which means certain, this is the verb version of that. So when you "do certain" you are going to make sure of something or you're going to verify something.
This one is kun'yomi followed by okurigana. If you remember the reading you learned with 確かに, you should know this one!
You should make sure the door is properly locked.