An unknown number of guns are being built with the mechanisms, causing problems for the police and ATF officials. Photo: An ATF agent holds a generic unfinished receiver, back, and one that has been manufactured, front, at an ATF field office in Washington, on May 06, 2014. The ATF is trying to crack down on the trade in the makeshift guns by targeting shops and individuals who offer to turn the unfinished receivers into functional pieces for firearms. (Photo by Bill O'Leary/The Washington Post)

The Komodo dragon (Varanus komodoensis) was the most popular species overall based on English language Wikipedia page views. It is the world’s largest lizard, living on the islands of Komodo, Rinca and other smaller islands, and on Flores island in Indonesia. (Photo by Eric Nathan/Alamy)

Ethiopian Airlines female pilots prepare the plane before takeoff at Bole international airport in the capital Addis Ababa, November 19, 2015. Ethiopia Airlines on Thursday, dispatched its first ever all-female operated flight. Every aspect of the journey was handled by women, from the ground crew, aircraft maintenance to traffic controllers. Gualu and her co-pilot were charged with flying the crew and passengers to Bangkok, Thailand. (Photo by Tiksa Negeri/Reuters)

A villa privately built on the rooftop of a residential building in downtown Beijing has prompted complaints from neighbours living below. Professor Zhang, the villa owner, has been instructed to tear down the illegal building, according to the property managers. (Photo by Mark Ralston/AFP Photo)

Grand Champion Oakhurst Crusin' in Chrome, an Australian Shepard, poses backstage at the Westminster Kennel Club Dog Show after winning best of opposite s*x on February 13, 2012 in New York City. (Photo by Michael Nagle/Getty Images)

Visitors of the world's longest tree top walk between the trees of the Bavarian forest on November 6, 2009 in Neuschoenau, Germany. The path, 1300 meters long and in 8 to 25m height, winds up to an impressive tower with a height of 44 meters. The wooden construction is integrated into the forest and delivers a natural experience. (Photo by Miguel Villagran/Getty Images)

Life reconstruction of the new oviraptorosaurian dinosaur species Anzu wyliei in its 66 million-year-old environment in western North America as seen in an undated handout illustration by Mark A. Klinger, Carnegie Museum of Natural History. Some 18,000 species, great and small, were discovered in 2014, adding to the 2 million already known, scientists said on May 21, 2015 as they released a “Top 10” list that highlights the diversity of life. Anzu wyliei, one of the top 10, dubbed “the chicken from hell”, is extinct. The feathered dinosaur whose partial skeletons were unearthed in the Dakotas was a contemporary of T. rex and Triceratops. (Photo by Mark A. Klingler/Reuters/Carnegie Museum of Natural History)

Sara Sampaio is seen wearing a pink knit sweater and a pink leather skirt during Paris Fashion Week Spring/Summer 2019 on September 24, 2018 in Paris, France. (Photo by Timur Emek/Getty Images)