I agree, i have worked several jobs that are extremely hazardous and much more deadlier than an oil rig and i was never restricted from carrying a knife. I have worked with brass tools in a explosive environment to keep from sparks and also in a suit in a 100 percent nitrogen environment to keep any sparks from generating but i still had my knife on me. This is why i believe the restriction was because of people injuring themselves from their own knives.