WhyExtHollow?

 From:  ACP (ALANCPIKE)
5887.1 
Hey can anyone check-out this design and tell me why it seems to extrude a hollow form and not a solid.. Then when I Boolean diff to get the shape needed for this soap dish that snaps on to a 1/2" GI pipe in the shower it doesn't work.. I save as stl and import to AXON 3 for 3d printing on my RapMan 3.2..
Anyone have ideas??

Thanks, Alan
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