Clone your image (Ctrl+K).
Select the Clip Tool (Two key presses).
Stroke your rectangle (Click-drag-release).
Click the Clip button (One click).
Hiding in plain sight. Explaining the Clip tool over the Rectangular Region tool is simpler.
Either approach is non-destructive as we have both produced clipped views that can be un-clipped anytime.
I still use the Cookie Cutter method more ofter:
Clone image.
Draw any closed shape.
Move behind.
Shift-click to select the on-top image with the underneath shape.
Q.
Acorn
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