To a Weim a fence is an obstacle to jump, climb, break through, or dig under.  Gates are for opening and Weims learn quickly how to work many kinds of latches. 

Their skills are also useful inside the house.  You may find yourself in the company of a Weim that you thought you had securely placed behind a gate, or shut into another room.  Some Weims are also good at letting themselves into or out of the house.

Window and door screens may be simply an annoyance to a Weim flying through the air on its way to the outside.