u/Reasonable-News-2346

50 catering boxes & 280 hot subs

I've replaced regular plugs & switches, but not a combo. I know about the main black/white/ground wires. My question is about the 2 black wires coming out of the plug itself. I'm assuming they're what makes the switch do its on/off. The old one is connected to 2 additional wires. What I need to know is if they have to be connected to a certain one like the line/load wires do or are they interchangeable since there aren't any obvious markings as to which gets connected to which. Thanks for any help!