Some of these weapons are signal pistols normally used by boaters and emergency signaling devices; magazine shotguns made from a magazine, electrician's tape, a machine screw, and a shotgun shell; pen guns made from modified tear gas devices; and the Glock 17, a semiautomatic pistol with a grip and trigger guard made of a high-tech plastic. Other such weapons are a ballistic knife that can fire the blade, plastic knives that are strong enough to be driven through a piece of plywood three-quarters of an inch thick, the sword umbrella, and a variety of office-pick weapons. Some unusual weapons include dummy grenades that can be made into fully operational fragmentation grenades and liquor bottles filled with gasoline or 100-percent alcohol. Some people also use the misdirection technique that magicians use to bypass countermeasures at a security checkpoint. Security professionals should keep abreast of the disguised weapons in use and keep line personnel informed through initial and ancillary training. Photographs.