| 摘要 |
PROBLEM TO BE SOLVED: To eliminate risks associated with the use of a conventional security chain between a jamb and a door at a doorway of a residence, such as the entrance, which risks arise from the fact that the security chain, usually consisting of one short chain, is often undone as a visitor requests. SOLUTION: A plurality of long chains, ropes or nets are stretched at a doorway of a residence such as the entrance to allow the resident to receive a visitor in a secure and open manner with mutual confidence, contributing to making a society that is secure and bright.
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