I am trying to edit an STL file to make it slightly wider at three different points on the object.

In the following image, you can see where I added three bisections and moved each piece the correct number of millimeters to increase the total width.

How do I add material between the sections to make the object whole again?

[![enter image description here][1]][1]


  [1]: https://i.sstatic.net/oLyhiBA4.jpg

Eventually, I'll export this to 3D print.