User Help > Managing Source Files as Members > Discarding Changes to a Member > To discard changes to a member’s working file in the GUI
  
To discard changes to a member’s working file in the GUI
1. From a Sandbox view, select one or more members that are checked out in your name or are modified.
2. Select Member > Revert.
If you have made changes to your working file, the Confirm Overwrite Working File dialog box displays. If you want to retain your changes in the working file, click No (No to All for multiple members). If you want to compare your working file with the revision you are reverting it to, click Differences. To proceed with the revert operation for a member, click Yes (for multiple members, click Yes to All).
The member is reverted to its original state prior to checkout.