A small mound or rounded hill.
"The somber tolling of the church bell served as a mournful knell for the fallen soldier."
A knell.
To ring (a bell) mournfully; to knell.
"The librarian knolled the new fiction section by placing all the mystery novels side-by-side and then stacking the thrillers perpendicular to them."
To arrange related objects in parallel or at 90 degree angles.
A surname.
"The new neighbor, Mr. Knoll, waved from his porch as I pulled into the driveway."