Joining Wires

[Unfabulous]

Heyo!
So I've got the smallest of problems that I thought I'd run past you.
I need to join some wires together, but not like you think. I'm not talking stripping and soldering, no sir, I'm talking side-by-side. It's better if I show you.

You also see it on fan cables and headphone cables a lot, stuck together side-by-side to create neat looking cables without the need for sleeving or cable ties or some such.
Is the pvc insulation melted together, or do they use some kind of pvc cement? I just don't know. I tried melting and joining but just ended up burning the casing and my fingers in the process. Lesson learned!

But as I say, it's the smallest of details that nobody but me is ever going to notice, but I just want it to be perfect so any help is appreciated.

 

[S_I_N]

all I can say is they are made like that and separated at the connections. So best guess is they have a jig that hold the wire then the put the melted insulation on it and it forms a ribbon of wires. Most likely a more sophisticated process but it shuld get my point across. I'm sure if you looked about on google you could find a similar wire and make your own with the proper ends and crimps