I think I spent three years in college getting examined on UML diagrams of all sorts. There is so much detail you can put into a UML diagram that means so much, like arrow heads mean class A implements interfface B. I have never seen anyone in work life ever use that much detail. I have done 100s of sketches of class diagrams and sequence diagrams but never have I made one that would fit the rigid rules of UML diagrams.How can there be so many rules for drawing lines between boxes?

I once did create fully compliant UML diagrams for a requirements document. The next day half the team emailed me back asking what all the box types, arrow heads and broken lines meant. Honestly, simple sketches with annotations have served me so much better than following the rigid rules of UML.