Here are a few options to choose from:

Check Plus is a line of credit that protects you from overdrafts by advancing your account money in case of insufficient funds. Application and approval required.
Set up automatic transfers from one of your deposit accounts.
At times, unexpected expenses or unforeseen circumstances can leave you with too little cash in your checking account. Having a check returned due to insufficient funds can be a costly, inconvenient, and potentially embarrassing experience. 
At Commercial Bank, we do not encourage overdrafts. As always, we courage you to manage your finances responsibly. However, we want to save you from the additional merchant fees and possible damage to your credit history that might result if a check is returned. That's why we provide Courtesy Advance, a special overdraft service for Commercial Bank customers.

Learn more about Courtesy Advance by viewing this brochure (PDF).