Download: http://archive.info-mac.org/gst/grf/rule-141.hqx
Rule is a tool to measure a size of an image on your screen. It has a
semi-transparent view and triangular shape. Easy to use just like the
one in the real world. Several units of length are supported. Many
convenient features are also available.
Info-Mac
The original online Mac user community. Bringing Mac users together since 1984.