Any idea what this screw is for?

[kbrose (Kyle J. Brose)]

Do you guys have any ideas why this screw might be on the breaker?

[rcooke (Roy D. Cooke, Sr)]

Just guessing loose breaker and screw helps to hold it tight .

[twitt (Thomas Witt, CMI MD. Lic. # 30933)]

Those are typically seen on mains.

[Jim_Port]

Breaker retainer screw used for some styles of backfed breakers. No issue.

[rmeier2 (Robert Meier)]

If the CB is back fed it’s required by the NEC to have a screw, rivet, clip or some other means to keep it from being pulled out.

[jjonas (Jeffrey Jonas)]

@Robert_Meier

If the CB is back fed it’s required by the NEC to have a screw, rivet, clip or some other means to keep it from being pulled out.

Really surprised Master Electrician, CMI, Roy Cooke didn’t know that! (No I’m not).

@rcooke

Just guessing loose breaker and screw helps to hold it tight .

[rmeier2 (Robert Meier)]

For the OP here’s the NEC reference:

408.36(D) Back-Fed Devices. Plug-in-type overcurrent protection devices or plug-in type main lug assemblies that are backfed and used to terminate field-installed ungrounded supply conductors shall be secured in place by an additional fastener that requires other than a pull to release the
device from the mounting means on the panel.