I am installing a inline thermostat. I have two wires that are hot (black) and two that are not (white) and copper ground. I'm looking for validation that the two hot wires get connected up to the "Line" on the thermostat, the two white get connected to the "Load" and the two ground get connected to each other.

If the whites are not hot, then they should be neutrals of a 120 volt circuit, and you cannot connect to stat as you explained.

What voltage are you dealing with?

I was a little off on the wires. One set of wires coming in consists of two (one white, one black) hot 120V (each) and a copper ground. There is a second set of wires coming in. Again, one white, one black, and one copper ground, none of these are hot and I'm assuming this set is running to the heaters. There are two wires out the back of the thermostat. The way I have it wired: I connected the two copper grounds together. I connected the two white (one hot, one not) together. I then connected the two black (one hot, one not) to the two wires coming out of the thermostat. The thermostat installation book says the two wires out the thermostat are not polarized. The thermostat and the heaters are working correctly, but is this correct?