This is a 1 min chart of the EUR/USD on 6 July 2018:
As we can see the lines are strong resistance points even on a 1 minute chart.
Tutorial for plotting these lines: https://steemit.com/forex/@gannamstyle/tutorial-analyse-any-chart-the-wd-gann-way-with-planets-and-get-rich-example-eur-usd