3D library parts of svg won't cut

[WillAdams (William Adams (Carbide 3D))]

Those are unjoined/unclosed/open geometry. It would be necessary to edit them so as to create closed shapes in order to use them for making 3D elements.

Please see:

Creating designs from elements

If one has a design idea one wants to make, usually it can be shown / mocked up as a pixel image, and put together using some basic elements. For example: [image2] All one should need for that is a portion of a U.S. flag, and the Marine Corps seal — fortunately, both are easily sourced on Wikimedia Commons: https://upload.wikimedia.org/wikipedia/commons/a/a4/Flag_of_the_United_States.svg https://upload.wikimedia.org/wikipedia/commons/b/b3/Seal_of_the_United_States_Marine_Corps.svg

which has some files which have closed geometry.