Delete Fencing

Guys,

I accidentally placed a fence in the wrong area, how the heck do i remove the damn thing lol very annoying.

Also i have a quest from the guard to deliver a letter, how do i do this? i go to the guy by the canon but he does no accept the letter or anything?

Thanks

Buy a hammer and drag it to the fence and for the letter, make the letter the active item and talk to the pink octopus alien