I picked up a cheap conversion on CL awhile back for a beater, but I was puzzled by this part:
http://www.imgur.com/34OaR.jpg
It seems to just be some kind of extra security just in case the wheel slipped in the dropouts? I googled around a bit and looked at sheldon brown, but I couldn't find any info on what it is and whether or not I need it. Thanks in advance.