After installing The Filter, with a pogo mod, it appeared that if center fans were guided by the two 2020 extrusions of bed, the sides one were only guided by one 2020 extrusion of bed and maintained by the pogo magnet.

I made it to have a wedge/guide for the other side. Check pictures for more informations.

Simple clip it into your 2020 extrusion, no need screws or nuts.

Will need two of these usually.