Need help identifying a part on a 2016 SR5 4x4 AC

Let's see if I can describe this exterior trim piece on my truck. Just behind the rear fenders wells are black plastic edge pieces that run from rear fender well back towards rear bumper. I would like to know what Toyota calls them. The reason I'm asking is because I'm adding Oem fender flares and mud guards. I think this mystery trim will interfere with the install. I looked at a truck with the flares and guards already on and that trim piece seems shorter as not to affect the flares. Hope this makes sense. Would have added photos but not sure how to do that yet.
Thanks in advance

 

Fender liner but have no idea of a part number

 

Thank you very much !