Yes, it's a wheel lock like strok said. It's the standard Dutch type with the key that stays in it whenever it is unlocked. It works well. My friend locked it before I could stop her and I was glad that it didn't get stuck locked! I was going to oil it first. What a nightmare had it been froze up and moved just enough to lock but wouldn't unlock!

I was imagining needing to get the dremel tool out and spending 10-15 little cut-off disks carefully getting it back off without damaging the frame or the paint.