What is a “Lifeline Extension Belt”?

Question

I was recently flying on an United Airlines A320 and noticed a narrow section between the overhead storage bins with a placard labeled "Lifeline Extension Belt" on it. It was over the wing exit row. What exactly is a lifeline extension belt?

Unfortunately I didn't get a picture, but what I'm referencing can be seen in these photos (not copied here since they are copyrighted):

• https://www.flickr.com/photos/oliverporter/7653848312 (on the top-left)
• https://www.flickr.com/photos/49111993@N00/13890509784 (narrow section is visible rising from the forward exit to the overhead compartment, no placard)

Answer 1

I think what the placard actually says is.

1. Lifeline
2. Extension Belt

(ie, its 2 things, not one!)

An A320 equipment specification indicates the narrow OHB you reference as number 16. Which is titled "Lifeline". This line is used to aid evacuation from the overwing exits and more details can be found in this answer

Extension belts are used for infants on their carers laps, an extra belt loops round the child and attaches to the carers lap belt.

_{(source: cabincrewsafety.com)}