This exercise pen is built from eight hinged wire panels, each 24 inches wide, finished in a black E-coat for rust resistance. The panels connect to form a square, rectangle, or round enclosure without any tools, and the pen folds flat again for storage when not in use. A step-thru door with multiple lock points and a slide-bolt latch allows people and pets to move in and out while keeping the enclosure secure. Ground stakes are included to anchor the pen to grass or soil when it is set up outside. The pen can also be positioned against a compatible dog crate to extend a dog's roaming space, with the crate sold separately. Panel height varies by model so an appropriate size can be matched to a dog's size.