picpac19 on Instagram: "The post features a 15-second video tutorial demonstrating the "fingernail test" for two-way mirrors: press a finger to the glass; no gap between finger and reflection signals a two-way setup, prompting users to leave for safety. on January 5, 2026, it amassed over 10,000 likes and 3 million views in 24 hours, sparking replies with additional verification tips like flashlight checks in dark rooms. The test relies on optics—normal mirrors have a front glass layer creating