A gongdao bei or fairness pitcher does what it's name says, makes it fair! You can pour the brew from your gaiwan or teapot into the pitcher then distribute tea between cups. If you are having a solo session, I still like to use a gongdao bei for several reasons. If I have a small cup, the pticher allows me to pour out my brew totally and then fill up my cup several times. The other benefit is that pouring from your brewing vessel to the pitcher then to your cups will cool the tea down a bit.