Replacing Electric BB Thermostats

Howdy all,
Here's my Joe Electrician story :)
Have electric basebd heat with wall thermostats, none of which have an Off setting. (house 40 yrs old)
I want to replace the wall controls with units that have an Off setting. Reason, two rooms are kept turned down as low as the dial will go, but can still hear a hum coming from both basebds during cold months. That's the why I'm doing this, to stop the flow of current at the thermostat.
Now, I now know I have single-pole therms and the ones with Off setting are dual-pole, which have four wires instead of two.
Therein lies my problem, I can put back wiring I take apart if it's the same, but since my knowledge of electrical wiring is on par with my ability to outwit that wascally wabbit and I don't want to burn the house down, which of the four wires from the thermostat go to the two black wires in the junction box?
The dual-pole therms have two red and two black wires. It appears a red and a black go to each ploe, is this correct? Which of the two black wires in the connectorbox is the "hot" wire?
....on the safety issue of this project....I do know to flip the MAIN breaker to OFF while doing my best impression of Tim the Toolman.
'preciate any help, thanks
YS
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It shouldn't matter which wire in the box is which. On the thermostat, 2 wires should be marked "line" and 2 should be marked "load". Splice the two line wires together with one wire from the box, and splice the 2 load wires together with the other wire from the box. By doing this you're using both poles of the switch as a single pole, utilizing the full amperage rating of the thermostat
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