How big would a reference surface be for a 120 inch straight edge.

[Dabbler]

Long straight edges come in a different format as well: I was assuming it was a parallel type, the kind I used when I was learning. The biggest one I used was 80 inches long, and had a parallel depth of around 12": when one of the other guys dropped and broke it, it was turned into 2 separate ones if different lengths, hence my question.

I've never used a camel-back version even though they are the most popular kind.