3 sided dogs runs are ideal when you have a existing wall that you can add your enclosure to. This helps keep the cost down. With our 3 sided dog runs 1 long side and 2 short sides are included. A gate panel and a Void panel is optional. (A void panel is a panel with a hole in it the allows a dog house to be fitted externally to the run and allow the dog access to the run area without taken up space in the dog enclosure).