Once my housekeeper said that she will open the cans with a knife I just decided simply again ordered these openers and given her.
After the first use, she reported that she had first thought that the opener is not working because it was so easy. You have then want to open the can on althergrachte way again with the knife and discovered that the can has been opened.
Only times as on the edge: on the can opener is a small gripper, with the lid of the can can be raised.