This system permits the outlet to grip the plug firmly and prevents it from slipping out as a consequence of its excess weight. In certain Exclusive sockets, a rod could be inserted into these holes to lock the plug when it is inserted. These holes also empower manufacturing unit sealing. https://types-of-electrical-plugs67776.blogdal.com/29765991/the-2-minute-rule-for-types-of-electrical-plugs-outlets