A ruler and measuring tape tool/brush, to be used for art or for estimating length of curves and shapes.
Ruler brush:
A tool I made to estimate the length of curves.The regular notch is 1 unit, the thick notch is 5 units, and the triangle notch is 10 units.

Example:

Line 1: The ruler tool applied to a curve, which measures the curve at almost 55 units.
Line 2: The measuring tape brush applied to a curve, with no background color. This is just a different style.
Line 3: The curve the other lines are measuring.
Line 4: Free-drawing with the ruler brush, which measures the curve at about 56 units (close!).
Measuring tape brush:
Using just the regular notched lines with a solid yellow background, this can be used for regular art.
Examples (with and without perspective):


Brushes