Abstract: A playpen structure which has a fold base which has first and second X-shaped joint/foot elements, first and second V-shaped joint/foot elements, four long bars and four short bars. Each X-shaped joint/foot element has a foot and first, second, third and fourth arms radially projecting from the foot. The first and second long bars are pivotally linked to the first and second arms of the first X-shaped joint/foot element. The third and fourth long bars are pivotally linked to third and fourth arms of the second X-shaped joint/foot element. The first and second short bars are pivotally linked to the fourth and third arms of the first X-shaped joint/foot element. The third and fourth short bars are pivotally linked to the second and first arms of the second X-shaped joint/foot element. Each V-shaped joint/foot element has a foot and first and second arms radially projecting from the foot. The first short bar is pivotally linked to the first arm of the first V-shaped joint/foot element.