Hello Folding Bike Forumers: I just bought my first folder. It's a Giant fd600. After some searching on the Web, I think that it might be called a Halfway, but I'm not sure. It's definitely an older bike. Measuring the diameter of just the wheel it's 12". The problem that I'm having is that I can't figure out how to lock the bike in place once it's folded down so that it doesn't keep unfolding when I pick it up. Can anyone help me out? Thanks!