I have a book on Sexing all type of fowl. The book says that you should vent sex the chicks 12-36 hours after hatching. Does this really matter? Can you vent sex older chicks? Also the diagram in the books makes it look like you need to open the vent to about 3/8 of an inch!!! It does not say to open it up that much butt maybe that is what you do? I really don't want to tear anything down there. So far I am really good at making Poo come out but I don't see anything that looks like a roo. I only have 4 chicks right now that I hatched but I can't imagine that they are all female. I have followed the directions but I'm not sure If I only caused a prolapse? The chicks return to normal just fine when I let them go. Not sure if I need to do more stretching and less pushing? Thanks for any replys.