"William R. Watt" wrote:

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

Sounds like it is Spanish Windlass time.

What he means is a loop of rope around the post twisted tight
with a stick of wood. You'll want to put wooden blocks under
the loops so the pressure is on the flat instead of the edge.

That only would work at the top of the post (which rises above the
wall portion in between the posts). And I'd rather use a bar clamp
(or two) there anyways and not a twisted rope.

Since it's impractical to rig something up to apply pressure to keep
the plank against the post (but I will have some screws to hold them
together), and since the plank is finished, stained, with a
polyurethane top coat (rigging something against it would likely mark
the surface), my original question is - does recorcinol glue need
bonding pressure in order to do it's job? I don't care how much I put
on in between the plank and the post (and I don't care if it bleeds
purple because it ain't gonna bleed through wood that's 15/16" thick).

This is not hard-wood I'm gluing together...