They both have a single vent. Kind of like a two roads converging into one. The butt and the genital eventually join at the vent so that's why sometimes their is poo on the eggs. If chickens mate their vents will touch but the rooster doesn't actually have a penis, sperm will just flow from the vent into the hen's vent.
![](https://previews.123rf.com/images/sietevidas/sietevidas1502/sietevidas150201136/36570834-multicolored-rooster-koh-samui-land-of-smiles.jpg)
bummer he got no penis though