https://external-preview.redd.it/DUraKIaUGyC3e_FNP_wZscbOELLt-Hrfz4MyKJmuTnQ.jpg?auto=webp&s=7cdef598f54d0c3c3cf54534423e6347ff287fc8

TIL Black Widow spider silk was used in WWII to create cross hairs in rifle scopes and periscopes.

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