# Bitcoin Fragment Sweep

<figure><img src="https://2242806881-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FevVaH47dfMmZxS9bt8lQ%2Fuploads%2FZ6hRrogKd9W3MKEe3aYN%2FBoomerang%20Sweep.png?alt=media&#x26;token=1574f8aa-c52d-45d7-987c-df0034c904c4" alt=""><figcaption><p>Sequence Diagram for SweepTx and RefundTx</p></figcaption></figure>

Intuitively, this sweep process works like commitmentTx in lightning, where the client always have an exit transaction available in case the counterparty refuses to respond.&#x20;

In Boomerang, before a Fragment signs on the SweepTx, the new Fragment Judge proposes a Refund Transaction on the previous state of the reserve. Once all the new Fragment signatories sign on the refund transaction, the Sweep signing begins on the unlocked Fragment address.