Fall stairs during the Spring Festival. Should I insert it vertically or obliquely?

Stick it vertically or obliquely, mostly obliquely.

Every Spring Festival, no matter in urban or rural areas, every household should take off beautiful red couplets and stick them on the doors to bid farewell to the old and welcome the new, thus increasing the festive atmosphere. Another source of Spring Festival couplets is spring stickers. The ancients posted the word "Yichun" more and more at the beginning of spring, and then it gradually developed into Spring Festival couplets, expressing the good wishes of the working people in China to ward off evil spirits and avoid disasters and welcome good luck. It is said that this custom originated in the Song Dynasty and became popular in the Ming Dynasty.