Used to decide who will give the right-away when two people with umbrellas are walking towards each other in a narrow passageway. Generally, the taller person should raise their umbrella to avoid collision. This changes in the case of mixed genders, in which case the male should go high.
Friend - Whoa! How did you know they would stay low?
You - Bro, it's simple umbrellaquette!
Stranger crashes umbrella into yours;
You - Whoa, learn some umbrellaquette...