The operation for double locking metallic handcuffs to be as:-

1. A mechanism which locks a handcuff pawl in an engaged position, and prevents the ratchet from advancing further in the closing direction.

2. A ring-shaped shackle for the wrist, usually one of a pair connected by short chain or linked bar.

3. A spring-loaded, pivoted bar which engages the teeth of a ratchet, permitting it to advance in the closing direction only.

4. A bar with inclined teeth designed to engage with a pawl. The ratchet should be free to advance past the pawl in one direction of motion only.

5. Weight : Not to exceed 425 g (15.0 oz)

6. Material: Rust proof stainless steel.

7. Dimensions: Each handcuff of each pair to have minimum opening of 50 mm (2.0 in) for insertion of the human wrist. The inside perimeter of the handcuff to be a minimum 200 mm(7.9 in) when the ratchet is engaged at the first notch entering the locking mechanism. The inside perimeter of the handcuff to be a maximum of 165 mm (6.5 in) when the ratchet is engaged at the last notch entering the locking mechanism. The maximum overall length of the pair of handcuffs to be 2400 mm (9.4 in).

8. Mechanical Strength: Each pair to withstand a maximum tensile force of 2200 N (495lbf) for a period not less than 30 Seconds, when tested. Not open under load, to show no sign of permanent distortion or fracture and to function in a normal manner following such test.

9. Corrosion Resistance: To show no substantial corrosion and to continue to function in a normal manner under exposure to saline spray.