[As far as canon is concerned, by Jedao's day they had a system using handwavy "gray goo" to seal shut any minor holes, which explains why everyone's wandering around wielding projectile weapons. We can handwave that even the very early heptarchate had it for simplicity of play. I'd have to double-check if "Chameleon's Gloves" says anything useful (which it might not), as I think it's the only thing set really early in the timeline--Kel, but pre-heptarchate.]