What do Bat droppings look like?
Technically called guano, bat droppings are about the size of a grain of rice. You can look all around your house or building, up and down. They may also lead up to a hole in the house.
How Small a Hole can they enter?
Bats can use a hole smaller than your pinkie to enter your home or building.
Bats can very easily enter a hole the size shown in this picture.