PICTURE 1 & 2
These are open knockouts (or twistouts). The cause of this condition is normally due someone removing a circuit breaker and leaving an opening.
This condition could allow for a number of problems to happen. Bees or other insects, mice or rats could build nests inside the electrical panel, water intrusion could occur, and/or children or adults could stick their fingers inside leading to electrocution, injury, or death. This could also allow for the panel to short circuit and possibly catch fire.
There is an easy and inexpensive fix. A small plastic or metal filler plate can be installed. The filler plate simply snaps into place. You don’t have to be an electrician to do this. However, if you are unsure, contact a licensed electrician to do the repair.