Objects disappear when adding boolean modifier I am following an example from a book using Boolean modifier to cut hole in an object. I have two 3D objects overlapping and when I apply "difference" operation, the first object disappears. It's only one edge of the first object that's causing this problem- when I move the second object to other edges it works.

I am very new to Blender, is there anyway I can attach my Blender file for all to see?
Thank you
The reason the boolean operation fails is because you have duplicated geometry.

Enter edit mode, press A to Select All, then press the Space Bar and type Remove Doubles.



The boolean should work now as expected:



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