A sheet of carefully selected MDF is gonna be
VERY straight. 1/2" or 3/4"... Rip a piece to the
size you wish making note of factory edge.

You "might" find a metal stud that is quite straight
also. These are a little harder to come by but can
be bought in most buidling centers.

Marton Czebe wrote:

I bumped into a problem this weekend. I needed a straight fence of
above 2.3 metres in length to do some edge routing. I couldn't find
anything in my small and basic shop that I knew was TRULY straight
across this length. (found some particleboard scraps about 2 metres,
but as I sighted down the long edge, I could see some dents, as well
as a small curve in it.

What do you people use as a reference straight edge? (preferably
something that stays straight for a while...iron, aluminium?)

thanks for your advice...

Marton Czebe