Where the shape comes from
An arrow shown just after landing, its point buried and its shaft still quivering above the line of the ground — the moment of arrival caught exactly as it happens. Add a roof over it and it becomes 室, a room, the chamber a person finally arrives at and stops; add a person standing beside it and it becomes 到, to arrive, reach, the plainer, everyday word for the same idea.
汉字 filed under 至
No published character on HSK Guide is filed under this radical yet. 汉字库.