Quote Originally Posted by Clive S View Post
How about using some fishing line stretched very taut along the length. ..Clive
Wouldn't that be a little flexible? Plus I've got an end stop on one end so can't wrap it round the rail, would have to accurately drill a hole through the steel.

Just looking at a Veritas straight edge http://www.axminster.co.uk/veritas-steel-straight-edge which I could clamp to the rail to keep straight?