Abstract: To address the protection gaps caused by repeated unhooking at intermediate supports of horizontal lifelines during work at height, this study proposes a non-release passable lifeline support composed of a steel pipe upright and a rotating cross turntable. Based on the principle of "spatial transposition and load-bearing relay," the support enables the safety lanyard to cross the support point while remaining continuously attached to the lifeline through the steps of pin removal, rotation, pin replacement, and resetting, thereby eliminating the protection gap inherent in the conventional "unhooking—crossing over—rehooking" operation. An overall model was established using Pinming Structure Software and verified under a 5 kN vertical concentrated load in accordance with GB 50017-2017, covering member strength, compression-bending stability, and key joints, together with field timing tests and cost estimation. The results show that the maximum bending stress of the main members is 167.99 N/mm², lower than the Q235 steel design bending strength of 205 N/mm²; the in-plane and out-of-plane stability values of the compression-bending members are 0.751 and 0.068, both below 1.0; and the checks of pin shear, hole-wall bearing, weld strength, and fastener slip resistance all meet the code requirements. The timing and cost comparison shows that the average passage time per support is about 7 s, approximately 133% longer than that of the direct unhooking method (about 3 s), while the unprotected exposure time drops from about 2 s to 0 s; the fabrication cost per support is 43.75 yuan (materials sourced from on-site surplus materials, counting only processing labor), about 55.8% lower than the 99 yuan per support of a dedicated non-release support with accessories. Trading a moderate time cost for continuous protection, the support eliminates the fall-risk exposure and features local materials, cross-site reuse, and economic feasibility, providing a practical solution for similar work at height.