While tape measures have all but replaced folding rulers for most tasks, there may be some time when a ruler is something you would want to use. Complimenting my post on tapes – here are some links to folding rulers:
I’ll start with some links to ToolGuyd’s posts:
Now some ones that I know about:
Doyle Log Scale
Engineer’s Scale
Plumber’s
Bricklayer’s
— Modular
— Oversized
Carpenter’s
Metric
Blacksmith’s