Product Details:

 This Miniature Circuit Breaker Lockout  is for use with all circuit boards, this MCB Lockout can be adjusted using a small screwdriver to fit securely on the circuit breakers. 

To use, firstly attach the MCB Lockout  to the circuit breaker, then use a screwdriver to make sure it doesn't  fall off the circuit breaker. There is a hole for an optional padlock to completely prevent the access.