If you turn the rule on edge to make your mark, all parallax is eliminated.
I have a 6 footer that I cut in two pieces so that I could have a folding
yardstick (actually two folding yardsticks.) I also have two 8 foot rules,
including a plumbers rule that reads inside.

"Richard" wrote in message
oups.com...
I've noticed that a folding carpenter's rule is often included in lists
of essential basic tools. I'm not sure I understand how a folding ruler
differs from a tape measurer. Could anyone explain what the advantage
of a folding ruler is?

Thanks,
Richard