I want this gun drawer!

I'll take one! I worry it would be too easy for the kids to figure out though.
 
Exactly. Also notice that he even hid the sides of the bottom drawer so there's no visible seam... Pretty neat!
Hidden yes but not that difficult in wood. Basically all he did was make the drawer side of the upper drawer act like the sides of the chest that the big drawer hinges are mounted to. Clean and simple which is always harder to do. That would be a neat feature to incorporate into a rear cargo box but if you did one out of steel or aluminum, the drawer slide mounting gets a bit trickier due to them being opposite each other and not a lot of room inside the inner slide for the nuts on the screws for the outer slide.