Circuit breaker and fuse lockout devices and systems prevent tampering or accidental equipment start-up. They protect workers from dangerous electric shocks. Clamp-on lockout devices are used on breakers that do not have holes in the switch tongues. They use a thumbscrew to secure over the tie bar and a padlock to lock the device. Pin style lockout devices use a push button to install onto a breaker and a padlock to secure the device and prevent tampering.