What does M, MU, and SLD stand for in the wiring from the Radio Receiver to the Amplifier in this wiring diagram?

http://www.alldatadiy.com/alldatadiy...7124/172768144

Basically, I'm looking for a switched power source to add a power outlet in my trunk (2011 IS250 F-Sport). I did find 2 non-switched power wires going to the amp, Red & Blue going into connector P27. I'm looking at connector P43.

Thanks.

Sorry, jumped too quick. Found it. Thanks.

why is this link being redirect to doubleclick?

Not sure about the link. It's suppose to go to a figure in alldatadiy. Maybe because it's a figure I linked to under my account, it doesn't show correctly when someone else tries to go there. The figure is part of the wiring diagram for the audio system w/nav.

I'm still looking for switched 12v power in the trunk area.