free-ruler

Install command: 
brew install --cask free-ruler

Name: Free Ruler

Horizontal and vertical rulers

https://www.pascal.com/freeruler

Cask JSON API: /api/cask/free-ruler.json

Cask code: free-ruler.rb on GitHub

Current version: 2.0.8

Current version requires: macOS >= 10.14

Analytics:

Installs (30 days)
free-ruler 28
Installs (90 days)
free-ruler 95
Installs (365 days)
free-ruler 430