Heater core inlet / outlet

[Matt24601]

I am hooking up the hoses for my heater and I was wondering which heater was the inlet and which one was the outlet.
2005 F-350.

 

[JLDickmon]

at the core, it doesn't matter.. but the inlet is usually the one to the inside of the vehicle..

 

[HeavyAssault]

Left side inlet.....right side outlet when looking at your photo.