Where no sheep would dare to go

 

This is a sheep ladder.  We see them when there isn't a gate in the fence that divides two grazing areas. 

Sheep don't like ladders, and won't use them even if the grass is obviously better on the other side. They're a bit sheepish that way. 

Mary doesn't like sheep ladders either, but she has things to see and places to go, so up and over she goes.