1. This rule was one the most complex produced by Pickett with 27 scales, or 31 if you count some of the scales with two sets of marking.
2. One feature is that the number of digits appropriate to different scales of roots is shown.
3. The rule has 2 full length square root scales and 3 full length cube roots scales, giving higher accuracy for these functions.
4. The rule has an ingenious system of lettering which enables the log-log scales to have double functions for numbers greater and less than one, shown below, by "pairing"  scales of the numbers greater than one with their reciprocals.