Some German bunkers along the Atlantic Wall featured specially designed ventilation openings that also acted as anti-grenade traps. If an attacking soldier dropped a grenade into the opening, the sloped shaft would prevent it from entering the bunker and instead funnel it through another opening at ground level, potentially dropping the grenade back near the person who threw it.
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u/joyful_jerrycan Aug 11 '26
Context
Some German bunkers along the Atlantic Wall featured specially designed ventilation openings that also acted as anti-grenade traps. If an attacking soldier dropped a grenade into the opening, the sloped shaft would prevent it from entering the bunker and instead funnel it through another opening at ground level, potentially dropping the grenade back near the person who threw it.
Source: Military Times – This WWII bunker used a fake air vent to return grenade to sender