hidden from the both sides

This kind of people are really very dangerous because they never show their bad face. They do such activities which are totally hidden from the both sides. The higher authorities and the subordinates can never notice their bad activities. This leg pulling always disturb the environment of the working places all over the world. At homes it can be in form of jealousy from each other between the family members. 

a tradition of some working places

Leg pulling is just like the backbiting and a social evil in all the communities. This is a tradition of some working places and I think this is also experienced at homes. When someone got high position or good position in the eyes of the higher others began to pull them down. Those who cannot bear the progress of their colleagues began to do some things which can stop their progress.