Can I use a plug without holes?

There is a hole near the tip of type A and B plugs. There is a reason why these holes are there. ... There are only two spring-action blades that hold the sides of the plug pin in some sockets. Since 1965, ungrounded type A outlets are not permitted anymore in new constructions in the United States and Canada, but they can still be found in older buildings. Type A and B plugs have two flat prongs with (often, but not always) a hole near the tip.