How to set Dirichlet BC at certain vertex

Hi all 
I am solving lid driven cavity 

I want to set a pressure value of zero at the bottom right corner.

I already was able to get the vertex number at that point.  But how can I set Dirichlet BC at certain vertex ? 


Thanks in advance 

Hi,
you have to set the freedofs bitarray at the dof number to False. As the first H1 dofs are exactly the vertex dofs it should be as easy as