Actually, they provide less security when used to replace, rather than supplement metal detectors. You can conceal a (sheathed) knife or (very small) pistol wit

Actually, they provide less security when used to replace, rather than supplement metal detectors. You can conceal a (sheathed) knife or (very small) pistol within your anus, with lube, patience, and some not inconsiderable discomfort. Neither will be detected by body scans, though they would be apparent to metal detectors. They are superior only in the very specific case of explosives or ceramic knives concealed under clothing.