Straighten, Square and Crop Photo's of Old Photos

[Ofnuts]

Use the perspective tool:

• Set to "Corrective" mode
  
• Drag the handles in the four corners of the image to the corners of what should be square.
  
• Confirm by hitting the "Transform" button.
  

[url=https://docs.gimp.org/en/gimp-tool-perspective.html][/url]