Inventor is a site that allows people to create things in 3D before they 3D print them out. It is simple to use when you get to know the site and you can make cool things on it.
Once you start inventor click on part,then standard ipt then start 2D sketch and pick on XY plane. Then click on the line tool and start to make this design.
Then when you are done creating it click on the dimension tool and you can go back and dimension the lines to proper length.
Then when you get done with dimensions you can extrude the drawing to 1 inch. Once you have that then hit 2D sketch and the side that does not have the little bump and click on it. Click on the line tool again and make the other sides piece.
Then when you are finished extrude the side to .25 inches, after that you will have a finished 3D widget .
Here is the printing preview before you 3D print, what you want to do is get a flash drive and connect it to the computer if your 3D printer is far away and then set it up to go to a 3D printer, and always print it to were nothing is printing free standing like the middle piece.
here is the widget in the 3D printer almost complete.