Select the button to view each example. If 3D PDF is in the title, click the button and if you have Adobe Viewer it will try to open the file. Look on the page for the download button. Click on the download button. Select Open file. hold the left mouse button down and move the mouse. The piece should rotate. Most of the files on this page will require Adobe Viewer. If you have Internet Explorer with the Adobe plugin, it seems to work correctly.