Re: help joining wood lengthwise
The first thing you should know is you don't need anything at all to glue that joint. Any of the options mentioned will certainly help with alignment and might make the glue up go easier but a properly done edge glue joint is stronger then the surrounding wood and doesn't need any special treatment. Do a search for the term "cauls" (on this site) and you'll find lots of good advice for gluing up table tops.
I agree about not using cedar for a table...unless it's a picnic table.
J.P. Rap Mount Hope Ont.
Carpe Ductum (Seize The Tape)
"In this world, you must be oh so smart, or oh so pleasant." Well, for years I was smart. I recommend pleasant. Elwood P. Dowd