I couldn't wait for UPS delivery so I used Rapidform's XOR to make a parametric model and then 3D printed up a set.

I designed these as four sided pyramids with a .75" through hole so I could insert 3/4" PVC or Black pipe, can't do this with three sided pyramids unless you use equal length pipes - not really adjustable.

Added three sided pyramid for comparison.

not much to say - just print it ...

"The usual way of finishing the top side immediately after bottom the is to flip the project and set it on a large board studded with nails. Painter’s Pyramids work the same way, but unlike nail boards, they can be moved around quickly for any size project, they won’t leave prick marks in the surface, and they nest into a neat, compact stack for storage."