It is for "fold position". when it is in fold-position, this piece can catch with a spring steel piece on rear seat stay. So the bike kind of in "locking position" for fold. you need to do some adjustment to achieve this. Once you you can used to you will know why and how!
Originally Posted by
Datatraveler
Thanks for the link biaddiction. There are some real beauties in there! I'm feeling lucky I found this little guy. Tomorrow it gets a bath and an inspection. Oh a question for you all, there is a little tab welded on the front post just below the reflector, what the heck is it for?