Help for assassins creed!!

I'm on the final mission in Acre, I'm at the docks and I need to scale a viewpoint to show objectives, the trouble is I get so far up the tower then it wont let me go any further. I can see where you are meant to climb up but it wont let me grab onto the...

stones that stick out the wall! Please someone hellp me with this its really *** annoying

I completed the game in like 3 days. Who are you supposed to kill and which district are you in, rich, poor or the or the other one? Help me to help you?

try moving around on the building because I have completed it and it has happend to me a few times

I've never heard of that. Just try moving around a lot near the stick you're supposed to grab or try to see if you can climb any higher. Just try to keep readjusting Altair, you might not have the right grab on the building to be able to reach the stick.

take the longer route and go all the way around to the left of the main tower