Q:

Basics!  How to get rid of protruding face that overlaps another object

A hopefully simple solution for a newbie like me.  So i created a cube, deleted the top face, and then created the roof using a single plane and mirror modifier.  Once i lined up the roof to the walls i had to fill in the space in the center between the roof and walls.  My solution was to extrude it up and then do away with teh excess face that is protruding passed the roof.  But to no avail i couldnt find anything... What is your guys's solution?  Or maybe a different method all around? 

A:

If you want to make a box with a roof, you can simply

add a cube
loop cut and slide it in the half like this:

select the middle top edge and move it upward

