Lew Hodgett wrote:

I don't think they make C-clamps with arms that are 8 feet long.

Sounds like it is Spanish Windlass time.

Aren't they used to pull things together? With rope? You can't push
with a rope.

I need to push a plank against a (verticle) post (assuming I really do
need the pressure for bonding with glue). I don't have access to the
back side of the post.