P was six feet tall and weighed approximately 265 pounds. The ground was covered with snow, but there was no precipitation, and the road was slick because the temperature had risen above freezing during the day but had fallen below freezing in the evening. P was driving home from work with his seat belt, a single device which included both a shoulder harness and lap belt, securely fastened as he had done so daily for six years. P negotiated an S-curve and was traveling at least 25 m.p.h. To avoid a collision with another car, he moved the 1987 Nova closer to the shoulder on his side of the road. P moved too far and slid off the road and hit two trees. The collision thrust P against the steering wheel, which broke, and the windshield, which shattered. At some point during the accident, the webbing of the seat belt separated while the female clasp (latch plate) remained fastened in the buckle. P sustained fractures to two bones in his lower left arm and cuts to his forehead. P sued Ds, the manufacturer, and seller. D removed the matter to the United States District Court based on diversity jurisdiction. The district court granted Ds' motion for summary judgment, dismissing the matter. That decision gave rise to this appeal. The district court struck an affidavit from its consideration and denied admission of the contents of the Nova Owner's Manual into evidence. The district court held that P did not raise a material issue of fact.