In the British Isles (and other regions of the world) drywall pens were built for sheep. In England they were called sheepfolds.
What the the advantages of this format over others in common use at the time?
For example as a shelter in a pasture to use for inclement weather? Or a convenient place to put all the sheeps while shearing? I don't know a lot about modern or historical livestock management to get more specific so I like to get an understanding of how they were used in medieval times.
ANSWER Thanks to Red Sonja, I did a search and found numerous allusion to the historical use of a sheepfold as a means of protecting a herd of sheep during the night from thieves and animals. Something that not stated in Wikipedia or various dictionaries. Or that you get by typing in just sheep fold back in 2014.
This is the clearest article I found.