For a boggy uterus, I bought a small soft Nerf ball and cut it in two (use a serrated bread knife). I also bought a small Nerf basketball for a contracted uterus. I then glued the bottom halves of small easter eggs to the bottom for the pelvic bones. I laid some soft fleece on the top for skin, and voila! This way the OB instructors can help the students differentiate the feeling of a boggy vs. contracted uterus.