Alright I give...how do I place a wooden door

Have tried every trick I knew in Terraria....including top and bottom planks, but my planks turn into a weird L shaped block when I try this

Still cant place a door...

 

You're probably trying it on the wrong size door frame, try making it one block taller.

 

there must also be material above and below it. I think the door is 4 blocks high.

 

Yeah, if you're used to Terraria, doors are not 3 blocks high, they're 4 blocks high.

 

They're actually five blocks high...

 

AH. I think I need to put material above and below.

Also...I take it RIGHT clicking while holding the material now fills in the area BEHIND you to make walls? Do monsters follow the same spawning rules ? (i.e. spawn where there is space behind you so you need to make a wall)