If you need to mark an Issue as blocked after you have created it, go to the details page of that Issue and then follow these steps:
The Issue is highlighted red and marked accordingly on the list that shows the existing Issues and throughout the current project to show that it has been marked as blocked – project members will still be able to perform actions on its details page. The reason of the block is shown on its details page under the Subject
Note: To unblock an Issue, go to its details page and, on the Sidebar, click .