Reply by lumbering_on

Spike, I’m glad to see you are going to be practicing your joinery.

That being said, end grain is a different animal. In this case, you are screwing through the face grain into either face or edge grain. If you think about the straw analogy, and imagine that you are pushing the screw across the straws, then you will realize that it will fasten the two boards quite securely. Just make sure that you drill a pilot hole or you could split the wood instead of pushing through it. see this video

https://www.youtube.com/watch?v=2rEqVvW75Q4

As for the size of the boards, you can certainly get away with a single 2×4 rather than two of them. Although, it’s not a bad idea to use the two as it’s easier to make it stable.