How to: Create triangles.

[Ming-Yan]

It's easier if you make the ramps first but it's essentially the same.
I make mine this way:

• You make a thin but long box and copy it 2 times. (3 left over)
  
• Rotate one of them to 45 and the other to -45
  
• now make a triangular frame [zoom in for more precision]
  
• Fill in the centre with "stairs" or until you fill on all gaps*
  
• Get rid of all the borders and anchor it all [or weld it together]
  

*You may have to add extra over lapping boxes.
**while building turn off physics.