Booby trap in the context of "Trapdoor"

Structures built by non-human animals, often called animal architecture, are common in many species. Examples of animal structures include termite mounds, ant hills, wasp and beehives, burrow complexes, beaver dams, elaborate nests of birds, and webs of spiders.

Often, these structures incorporate sophisticated features such as temperature regulation, traps, bait, ventilation, special-purpose chambers and many other features. They may be created by individuals or complex societies of social animals with different forms carrying out specialized roles. These constructions may arise from complex building behaviour of animals such as in the case of night-time nests for chimpanzees, from inbuilt neural responses, which feature prominently in the construction of bird songs, or triggered by hormone release as in the case of domestic sows, or as emergent properties from simple instinctive responses and interactions, as exhibited by termites, or combinations of these. The process of building such structures may involve learning and communication, and in some cases, even aesthetics. Tool use may also be involved in building structures by animals.

An improvised explosive device (IED) is a bomb constructed and deployed in ways other than in conventional military action. It may be constructed of conventional military explosives, such as an artillery shell, attached to a detonating mechanism. IEDs are commonly used as roadside bombs, or homemade bombs.

The term "IED" was coined by the British Army during the Northern Ireland conflict to refer to booby traps made by the IRA, and entered common use in the U.S. during the Iraq War.

The Inner German border (German: innerdeutsche Grenze or deutsch–deutsche Grenze; initially also Zonengrenze, "Zonal boundary") was the border between the German Democratic Republic (GDR or East Germany) and the Federal Republic of Germany (FRG or West Germany) from 1949 to 1990. It ran north-south in a 1,381 kilometres (858 mi) long, irregular L-shaped line from Dassow at the Baltic Sea to Eichigt at the border with Czechoslovakia. The better-known Berlin Wall was a physically separate, less elaborate, and much shorter border barrier surrounding West Berlin, more than 170 kilometres (110 mi) to the east of the Inner German border.

The Inner German border was formally established by the Potsdam Agreement on 1 August 1945 as the boundary between the Western and Soviet occupation zones in Allied-occupied Germany. On the Eastern side, it was made one of the world's most heavily fortified frontiers, defined by a continuous line of high metal fences and walls, barbed wire, alarms, anti-vehicle ditches, watchtowers, automatic booby traps and minefields. It was patrolled by 50,000 armed Border Troops of the GDR who faced tens of thousands of West German, British and US guards and soldiers. In the hinterlands behind the border, more than a million NATO and Warsaw Pact troops awaited the possible outbreak of World War III in Europe. It was a physical manifestation of Winston Churchill's metaphorical Iron Curtain that separated the Soviet and Western blocs during the Cold War. Built by the East German government in phases from 1952 to the late 1980s, the fortifications were constructed to stop Republikflucht, the large-scale emigration of East German citizens to the West, about 1,000 of whom are said to have died trying to cross it during its 45-year existence. It caused widespread economic and social disruption on both sides; East Germans living nearby suffered especially draconian restrictions.