[krolley]

In Switzerland, when you pass by a building site that has opaque boards up around the perimeter, they often have a little hand-sized cutout at eye level so you can have a peek inside. It's strange, and I assume it is for the curious to have a look, not sure.

[therealdrag0]

Some fence holes are to allow wind through and reduce the sail effect. Not sure if that applies to your reference.