Level Editor "Locking" question

[Nye]

Each set (castlebase, mansionbase, dungeonbase) etc. has their own welders. You slap them between two walls, or in corners, to make the place look better and hide weird looking corners (eg. when a corner is formed from two castle walls).

||||||||||||||||||||||||||||||||||||||
||||||||||||||||||||||||||||||||||||||
----------------------------||||||||||
------------------ <-Here-||||||||||
|||||||||||||||| |--------- ||||||||||
|||||||||||||||| |---------- |||||||||

^ supposed to be a corner round a bend (aerial view)