I have a Manfrotto 680B that has been slipping down on me during the last few weeks. After some research, I've learned that I could fix this issue with the little plastic wrench that came with the monopod. The problem is, I have no idea where I placed that wrench. I've read that I could use some type of hex wrench, but in looking at the top clamp on the monopod, where it needs to be tightened, I can't figure out where I would tighten this. Can anyone help me?