Lego Stacked Sticks Interlocking Puzzle

This puzzle slides together quite easily, if you know the trick! Try to put the pieces together in the wrong order and they will block each other from interlocking. 

You will need:
-128 1x2 plates
-12 2x2 plates
-52 2x2 tiles

Each piece that you need to make will be a 2x8 stick that is made of a combination of plates and tile. There is an entirely smooth one, and two types with a 2x2 plate on them, either at the very top or two studs down. The picture shows all the parts you need to make. 

Each part is made of of 4 of these sticks, 3 with a 2x2 plate and one smooth one on top. 

Follow the pictures to build Part A.

Follow the pictures to build Part B.

Follow the pictures to build Part C.

Follow the pictures to build Part D.