Just from what i read when they start to pip then pull it if not before. Some pp l say on here  they dont ever put them in. the bator co said to have it in until pip.I have kept my hole covered  with tape 3/4 of the way and the other is covered with the fan exaust. To get the humidity up though i covered it all the way.I keep reading  here they need air to breath once they pip have to open them all.
If you have one rocking then they are on their way!! EXCITING!!
.Day 20  for me this morning and all is quiet with mine
If i see any movment i think i willl cry I think  i will be so happy as i am not confident any will hatch ..One eggs looks in a different position than last night but i bumped the table too a little so Maybe i didnt notice the change in position then.
 Just Wishful thinking!. GOOD LUCK!!