Question: I work with reconstructing fossil skeletons of human ancestors. Bones are usually incomplete and I need to assemble whole virtual bones from laser scans of different fossil parts of the bone I have scanned. How can I efficiently delete parts I don't need so that I can assemble whole virtual bones? I know it's easy to delete by bisecting, but that's not enough for what I need [![enter image description here](https://i.stack.imgur.com/zYOwO.jpg)](https://i.stack.imgur.com/zYOwO.jpg)Does this image help explain what I wantto do?

Answer: 
Hope this helps:

You can try centering the mesh in an axis (X or Y most commonly) and then use `numpad 1` or `numpad 3` to get an isometric view of the mesh along that axis. (Depending on your blender config, you might need to also press `numpad 5`)

Then you can press `z` and `tab` to go into wireframe mode and edit mode respectively.

Once there, you can select whatever vertices are not needed (To select vertices you can use the hotkey `ctrl`+`shift`+`tab` and select vertices in the popup menu) and delete them. Then press `tab` again to go back to object mode and add a mirror modifier to mirror the whole "correct" side of the mesh along the axis you need. Fiddle around with the merge and clipping options to get whatever desired effect you were looking for.
You can use `Shift`+`Ctrl`+`Alt`+`M` to select non manifold vertices, essentially finding all holes and floating vertices in a mesh.