Kumi kata, gripping, is essential in judo for both applying techniques and defending. There are two basic forms of gripping:
Ai yotsu, same side, where both players grip in a similar fashion (e.g. both players' right hands on the lapel and both players' left hands on the sleeve.
Kenka yotsu, opposite side, where each player takes an opposite grip (e.g. player one places their right hand on player two's lapel and their left hand on player two's sleeve. While player two places their left hand on player one's lapel and their right hand on player two's sleeve.