hope this link helps Nissan In-Cabin Microfilters Installation Instructions - page 2 of 3
Dirty side up, airflow indicator down.On 2nd gens, which way do they go in? Which way is the air flow? Up or down? I feel like an idiot for not knowing this. Duuuuhhhhh........
I did that with my last Frontier. I ended up getting a small bolt with wing nut....worked perfectly.I busted mine. Holding on with electrical tape for now. There is an eyelet in the molding of the filter housing and access door that I will put in some type of fastener eventually.
I changed mine and was not sure on the air flow, so i turned on the blower. Stick your hand in (be carful and keep it where the filters go) and feel the air. Thats all i did, be careful as you can break the plastic tab pretty easily, mines not hanging on by much.