You can convert the ball into a wheel by putting a coat hanger through a small hole near the entrance and the back of the ball. The Ball can then be suspended from the lid. When the gerbil wants to run it will jump into the ball, when its finished it will jump out. See--http://www.geocities.com/Heartland/Estates/4185/dig/ballwheel1.jpg http://www.geocities.com/Heartland/Estates/4185/dig/ball2.jpg -- Gary's web pages - http://home.talkcity.com/StudioDr/go5
