I have a hard trifold but it won’t fold up along the widow so blocks tall things at the front third of the bed.
I recommend that you look at some motorized version since the trifold is either closed or open and not really that easy to open to sit stuff in the bed. You have to open the tailgate then open the cover if you want to sit something fairly close to the front of the bed.
I also recommend that you get a latch system that can release both sides of the cover at the same time. Mine has a separate handle on each side of the two folding sections so you have to walk back and forth to undo (or redo) the latches.
I remember that WeatherTech had a nice one but it was pretty costly, and I don’t think it was motorized either.
To add a few other thoughts to my previous post above…
The actual brand on mine was AutoSaver88 and here is a link to the one I bought for my 2016 Nissan Frontier.
The truck has a factory rail system for attaching the tie downs and adjusting the bed extender. The cover was selected because it uses the rail system as the attachment point. I am not sure how it would attach to the truck if you have the rail and bought the standard attachment method. In other words if you have a rail system in your truck you need to figure out how the cover mounts to the truck and see if there are interference problems with the rail system. The cover makes the rail system difficult to use due to the attachment method being in the rail, limiting where anything can be moved towards the front or the rear. The floor rails are still completely free though.
The sealing system at the front is very similar as shown in the video by Sidekick above. But one additional thing that is on mine is a heavy rubber flap attached to the cover that is folded down into the space between the cab and bed. It provides a drip shield as well as covering the gasket and blocking air driven water from the gasketed joint between the bed front and cover. It works very well. The sealing along the sides and rear end are a rubber circular section that is pressed against the plastic bed rail covers by weight and the attachment system. It seals fairly well, not 100% watertight but only minor water has gotten in the bed during heavy rain and highway speeds for miles of driving.
The main complaints I have are:
The separate holdown latches (6 total with 4 being quick release style) so you have to walk back and forth to release them to fold up the sections. The tailgate must be down to open the cover and to lock the cover in place. The tailgate lock makes it secure.
The placement of the latches and attachment points interfere with the rail system so make it somewhat difficult to use well. The rear bed extender is very difficult to use unless it is stored separately and the attachment is left behind at the very rear of the truck rail system. (These have to be installed and removed from the very front of the bed which requires all the cover attachment points to be removed and the cover lifted off the bed.)
. Plus it tows like a V8 with all the gears. You need that extender when you only have a little one 
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