kakashi used kamui to warp things away into another dimension. he did that opening a small hole into our dimension and warped thing in there( deidaras arm/explosion, the nail which was thrown at him by pain and the rocket, sasukes arrow etc) since his eye used to be obitos it is connected to the other eye( meaning to tobis sharingan) whenever something is about to hit tobi he removes that part of his body to the other dimension( which is where also kakashi sent things) thats why when he dodged naruto he got hit by the flying kunai which was warped away earlier by kakashi..sounds pretty confusing but it actually isnt^^ hope i could help