How to choose appropriate anchor points to maximize security when using chain locks?

1. Select structurally sound locations with clearly defined load-bearing capacity.

Chain lock anchor points should be placed on load-bearing components such as walls, door frames, or metal brackets, avoiding the use of thin decorative surfaces or soft materials.

According to the *Construction Handbook (Sixth Edition)*, the arrangement of chain lock anchor points should meet the accuracy requirements of "centerline overlap ≤ ±1mm, guide rail vertical position ≤ ±2mm, guide rail front-to-back position ≤ ±2mm" to ensure a tight fit between the lock body and the base.

2. Reasonable spacing and number.

For scenarios requiring long chain coverage (such as bicycles, doors, windows, and fences), it is recommended to use at least two anchor points to form a triangular support structure, which can distribute tension and reduce stress concentration at single points.

The *Specialized Construction Plan for Supports* suggests: anchor point spacing of approximately 600mm, with the upper and lower anchor points 150mm and 200mm from the boundary respectively, ensuring even stress distribution.

3. Select Appropriate Fasteners

Common bolt sizes: M6, M8, M10, M12, M16. A standard quantity of four bolts is typically used, providing sufficient tensile and shear strength.

For high-security requirements (e.g., industrial doors, warehouse entrances), high-strength expansion bolts or stainless steel screws can be used. Torque calibration should be performed after installation to prevent loosening.

4. Consider Using Anti-Pry Structures

The chain lock's head is made of high-hardness heat-treated steel (HRC55-60) or carbide steel, possessing excellent shear resistance. Combined with anti-pry lock body designs (e.g., thickened bolt tongue, internal anti-drilling structure), the level of protection can be further enhanced.

5. Check Post-Installation Stress

After installation, a tensile/shear force tester (e.g., applying a 10kN preload followed by an 8kN horizontal forward force) can be used to conduct on-site acceptance testing of the fixing points, ensuring that the actual stress does not exceed the design safety factor (generally twice).

Practical Recommendations: When using chain locks at residential entrances, install the fixing points on the top and bottom sides of the door frame, approximately 400mm apart. For warehouse or industrial entrances, use three-point support (left, right, and top), using M10 expansion bolts at each point with a 600mm horizontal spacing for optimal stress distribution.