Four Interlocking Triangular prisms designed by Daniel Kwan. His mesmerizing work here : https://www.flickr.com/people/8303956@N08/
It's easy to make the units. I had trouble assembling the first triangular surface (a prism has three rectangular surfaces and two parallel triangular surface) of the prism. The flaps tucked in would come out and had to start from the beginning. I had the same issue last year sometime when I tried and had given up on this model. But finally now am able to complete it.
Assembly to interlock each prisms is not so difficult to figure out though.
A very nice tutorial by origaminut
Paper used : color printer papers
No. of units : 12 square sheets (3 square sheets per color)
Paper size : 8.5 inch square
Difficulty : Intermediate
(16 May - 17 May 2014)
Group photo of the interlocking types of modular origami:
From left to right : four interlocking triangular prisms, three intersecting rectangular rings, five intersecting tetrahedra and nine intersecting planes