B-17 question

[BobP]

A friend sent me this picture with the question of what the black lines mean? Seems there were some B-17's with these marks on them. I have no clue as to what they are for but I know that with the knowledge of the folks in here that someone will have the answer.

[clipper1801]

Lines on the wings mark reinforced areas for walking on. Black on the leading edges are deicing boots.

[BobP]

I thought it was something like that but wanted a sure answer. As I said I know someone would know. Thanks

[BobP]

Turns out my friend was testing me and pointed out that these were Lockheed Vega planes with the markings on them.