MacBook: My Documents and Application folder back to the Dock

I accidentally delete these 2 folders from the dock and have been trying for the last few days dragging it back from the Finder to the dock and it just poof! goes into the trash. I have to go back to preference and check the Application to see it again. Anyway I found out how to put these 2 back to the dock so it stack. Drag to the right side of the dotted line and you can see how the trash can kinda move over to make room. Then only you drop and it won't go into the trash. This small detail cause me sooo many hrs of frustration and its just so easy. Ah, the surprises of MacBook, never-ending...