How do I make all these faces lay flat ? without changing the scale? I might just be overlooking a really obvious way to do this, but here's my issue. I want to make all of the triangles shown here completely flat. I know I could just scale them along the z axis but they need to be the exact size they are now.

This is the project I'm working on:



This is the top view of my project. They all look fine from here, but when you look at the side view:



You can see they're all at different angles. So is there a way that I can make them all completely flat without changing the scale?
First create a plane that you would like to align them all to. 

Second If they are not already individual objects, go into edit mode and hit P to separate by loose parts. 

Then enable snapping by clicking the magnet button and set up the settings as you see here:



Finally, select the parts in object mode hit G to move them. Put your cursor on the plane, then they should rotate to match the plane.