He examined it distrustfully. He had always considered the bolt anti-grav the most unreliable of anti-gravitic devices. The anti-gravs in commercial use (most strictly supervised, since geeksters and raubsters had discovered their value in mass levitation of stolen goods) were perfectly safe. But the bolt anti-grav worked on a different principle. Its "doughnut" discharge produced what non-material physicists called a reversed stasis of the object which it hit. The object in consequence became weightless. The difficulty was that there was no practical way of estimating in advance when the stasis would return to normal and the object acquire weight again. And, since stasis reversal was potentially harmful to living tissue, all bolt antis had built-in governors preventing their discharge too frequently. Too dangerous for a children's toy, too ineffective for genuine use, the bolt anti was the perfect example of ingrown gadgetry.