WASHINGTON  The newest tool at airport security checkpoints is 3 inches long and costs only a few dollars: a handheld black light. Airport screeners are starting to use them this month to examine driver's licenses and other passenger ID cards presented at checkpoints to spot forgeries or tampering. Passengers with suspicious documents can be questioned by police or immigration agents. Black lights will help screeners inspect the ID cards by illuminating holograms, typically of government seals, that are found in licenses and passports. Screeners also are getting magnifying glasses that highlight tiny inscriptions found in borders of passports and other IDs. About 2,100 of each are going to the nation's 800 airport checkpoints. The closer scrutiny of passenger IDs is the latest Transportation Security Administration effort to check passengers more thoroughly than simply having them walk through metal detectors. In the past six months, the agency has been taking over the checking of passenger IDs and boarding passes at airport checkpoints. For years, security guards hired by airlines have done that. "This is a significant security upgrade," TSA chief Kip Hawley says. Screeners are trained in spotting forged documents and will get some training in studying suspicious passenger behavior to pick out people who merit deeper scrutiny at the checkpoint, Hawley says. The TSA screeners, unlike security guards, also get daily briefings on the latest airport security concerns. More than 40 passengers have been arrested since June in cases when TSA screeners spotted altered passports, fraudulent visas and resident ID cards, and forged driver's licenses. Many of them were arrested on immigration charges. Airport security consultant Rich Roth says screeners will do a better job than security guards checking identification because they have training and "a little more authority" to question passengers. Airlines welcome having screeners observe passengers while checking their IDs and boarding passes. "That's the kind of resources the TSA can devote to the document-checking that the airlines didn't," says David Castelveter of the Air Transport Association, a trade group of major U.S. airlines. The TSA has taken over document-checking in about 400 of the 450 airports where it operates. The agency will take over the remaining 50 in the next couple of months, TSA spokeswoman Ellen Howe says. Conversation guidelines: USA TODAY welcomes your thoughts, stories and information related to this article. Please stay on topic and be respectful of others. Keep the conversation appropriate for interested readers across the map.