bookmark, guidebook
栞 centers on a physical marker that guides or holds a place: a bookmark in a book, or by extension a guidebook that marks a path.
栞 is a Japanese kokuji (国字) created from 幵 (a variant of 干) and 木 (tree), likely representing a wooden marker or guidepost. The exact historical development is uncertain.
The top part 幵 looks like a marker or sign, and the bottom 木 is a tree. Imagine a wooden sign stuck in the ground as a guidepost, or a wooden bookmark marking a page.
For カン, picture a can of wooden bookmarks: can -> カン, and you pull one out to mark your page.
bookmark