This is in continuation with Part 1, here is another method to cut a diagonal on a cuboid
1. Open the existing file or create a new file and model the cuboid.
2. Start 3D sketch.
3. Select Line command.
4. Select any one vertex of the cuboid.
5. Start the line and while in line sketching mode, select the second vertex.
6. Continuing with the sketch, select the third vertex.
7. And finally select the first vertex you started sketching with.
8. The final sketch will look like in the picture (might differ if you have a different sized cuboid).
9. Now click on point command.
10. Create a point on another vertex (leaving the three vertices used above).
11. Exit sketch mode and switch to loft cut (select from toolbar or Insert > Cut > Loft cut).
12. Select the 3D line sketch as first profile and point as second profile. If you have the “show preview” selected, you can see the preview.
13. Select point as second profile. If you have the “show preview” selected, you can see the preview.
14. Click OK and end result will be the diagonal cut.