How do you use the small pen hook inside the 5-Year Techo cover?

It has a diameter of 8mm^[1][2]. This means it is too narrow to fit the whole pen body through, so only the writing instrument's clip should be hooked over it^[3][4].

Hobonichi designed this loop on the inside right side of the cover so a pen can be hooked by its clip^[5][6][7]. Storing the pen hooked on the inside rather than exposing it to the outside keeps the exterior neat and tidy without bulging when the planner is closed^[8]. However, as the loop has a diameter of 8mm, pens with exceptionally wide clips may be difficult to insert^[9][10].