Stuck Together like Bricks and Glue

Friends
They are strong bricks
Holding each other together
Though one may break in places

But then there's me
I feel as if I'm the one stopping them
Sitting on top of the brick wall
Leaving only my presence there as I leave

Does the wall crumble as if from age
After I leave?
Does my absence somehow leave
Them actually needing me?

All in all
Not just another brick in the wall
All in all
Not just another brick in the wall

Not I, for I was always just a brick
Though sometimes I seemed alone
Sitting there, amoungst others
Though we all thought we were alone

But there was one other
Who's absence would leave
Me needing, falling, breaking apart
Nothing the other bricks do would hold me in place

My Cornerstone, My All in All