The design allows for some flex in the holder to make pressing it in easier. Inserting the Sharpie / marker presses the holder outward securing it further. With a well balanced roll, perhaps you will have a large top to spin ;)

It is also possible to tie a string around the marker and the other end to the holder to ensure they are always together.

A version without a spot to store the cap is included (and reminds me a bit of a tie fighter). This may also be handy as a hub for storing the roll on a peg or length of rod, perhaps even as part of a large, multi-roll dispenser.

This is remixed from my surface mount Sharpie holder. Check it out if you need to keep one handy on a wall, tool box, or another flat surface: https://makerworld.com/en/models/19779