[amitmishra4]

Presuming you are inserting them in the slots the correct way, they should simply click without much hesitation. If they aren't, I'm thinking maybe the locking mechanism was broken by a previous owner? They are quite a fight to get out. I think I got cut up while removing mine. Fellow members have suggested using two screwdrivers to pull the unit out for easier grip. The locking mechanism allows that kind of force to be exerted on itself. Inserting them back was pretty painful for me too and at one point I was pretty frustrated, enough to snap the locks off. Other people suggest it slides in no problem. Explore the idea it may be broken.