the rear OEM Floor mat keeps sliding forward over time and was getting quite annoying.
design this clip to prevent the mat from sliding.
the one that i am using, and i think is the best is the Angled-Notched.stl version
Floor Mat Retaining Clip Rear Mazda Mazda3 3rd gen BM BN Series 2013-2018 Angled-Notched.stl
other iteration also provided in case those fit better for your situation
to install, put the mat in the clip first, then push the clip bellow the car seat rail.
only tested on a Mazda Mazda3 SP25 GT Manual 2016 BN series
should work for the other variant and for the BM series as well. if you do test it, please comment and let us know
FreeCad 0.18 design file also included