Canon RF 35mm F1.4 L VCM Instructions Manual page 18

Filters (Sold separately)
Attach the rear filter holder to the back of the lens.
Align the attachment position mark on the lens body with the index on the rear filter holder.
Turn in the direction of the arrow until the rear filter holder index aligns with the stop position mark
on the lens body.
Attachment position mark Index Stop position mark
ENG-17