On 7/18/2012 2:19 PM, dpb wrote:
.....

Measure, drill, dowel, measure..."I wonder if the RO is
square"...Glue, clamp, measure, adjust..."I wonder if the RO is
square"...Glue, clamp, measure, adjust..."I wonder if the RO is
square"...carry it up the stairs, go have lunch..."I wonder if the RO
is square".

Of course, maybe that's just me.

That's just you...
....

But to make it perfectly clear--the objective is _NOT_ to force the door
to measure the same across the two diagonals _UNLESS_AND_ONLY_UNLESS_
the measurements of the door show it has _NOT_ been trimmed
significantly to compensate for an out-of-square opening.

If the lengths and widths are uniform then the door has not been
significantly altered and that's the indication when it has been brought
back to square, yes. If those measurements show it has been trimmed
significantly, then the point (and really the point anyway) is _still_
to get the rails and stiles back to their original positions and full in
contact w/ the coping having removed all the accumulated dirt, paint,
etc., that has built up over the years. The diagonal measurements then
will not necessarily be the same but it won't matter. The point is the
door will be back to very close to the dimensions it was before it
failed badly enough to be a problem.

In actuality looking at the pictures OP posted when it was down and
partially apart, the top rail, lock rail and quite possibly the next one
down show little evidence of separation--the "sagging" is almost all
solely in the bottom kick stile joint(s) which has/have come loose and
the subsequent wear on the dowels and dowel holes in it that cause it to
droop. When that panel is back in it's proper place or near to it, I'd
lay pretty good odds it'll fit the opening just fine w/ perhaps just a
little tweaking...

--