"I'm not really sure what the three angled lines mean"
Meant to be pryed upward......there's a little (very little) tab on one side of the end of the handle.....you can just barely see the slot for it on the left side hole in the drawing.....
Pry "apart" sort of, then rotate the handle 180 degrees so that little tab will slide out thru the slot........
They are a pain until you do it once, then it seems easy.......possible someone pushed it thru the wrong side somehow & it's a bit jammed, combined w./ rust doesn't make life easy !!!
Maybe hit it w/ WD40 or some other rust dissolving compound & let it sit awhile?
I don't so much like using obnoxious chemicals where food will later be prepared, but sometimes it's warranted !!!!