On this example
you can see a slight countersink on the bronze bushing. This
side of the rod will go toward the throw or the cheek of the
crankshaft. The countersink is there to clear the small radius
left when the crankpin is precision ground.
I have seen some
rod that are countersunk on both sides. In this case if the
oil holes are symmetrical the rod may be placed either direction.
If the oil holes
are not symmetrical I usually suggest that the oil hole should
go in the direction to pick up oil on the upward stroke. Although
some people argue to the contrary.