If you participated in a Lockdrop event and your lock duration has ended, you can use the Unlock tool at Commonwealth.im to retrieve your ETH. Simply send a transaction with a value of zero or greater from any account to the contract address of the Lockdrop User Contract (LUC). The LUC will then return your ETH to the original address that sent it to the Master Lockdrop Contract at the beginning of the event. For a more detailed explanation, you can check out the blog post at Blog.edgewa.re.