I've always tried to get the bump when I flat iron and I've never been able to get it until I found this YT video. I think she's a hairstylist and she explains the technique very well. I am sharing because I guess there may be some of you girls who never figured out as well. Hope that helps 
http://www.youtube.com/watch?v=7G0xJo1hv1c&NR=1
http://www.youtube.com/watch?v=7G0xJo1hv1c&NR=1

......off to YT......
I tried it a couple of times and my hair was always straight. I do cross-wrap sometimes to protect my ends while I am sleeping, I never got the bump. I just don't know what I am doing wrong