What the square snaps to before the first click

• To a wall face. The square sits flush against the face, and the wall will start from that wall.
• Past the end of a wall. If you bring the square to the free end along the axis, it will extend the wall.
• To the middle of a wall. A triangle appears.
• In line with the edges of other walls. A dashed guide appears.

A square that has touched a wall is always connected to it. There is no next to, but separate position, so the room closes.